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  • Zea mays  (394)
  • Springer  (394)
  • American Meteorological Society
  • 1995-1999  (201)
  • 1990-1994  (193)
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  • 1
    Electronic Resource
    Electronic Resource
    Expression of MADS box genes ZMM8 and ZMM14 during inflorescence development of Zea mays discriminates between the upper and the lower floret of each spikelet (1999)
    Springer
    Development genes and evolution 209 (1999), S. 411-420 
    Details
    ISSN: 1432-041X
    Keywords: Key words Flower development ; Floral determinacy ; Spikelet ; MADS box genes ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Most floral meristem and organ identity genes of dicotyledonous plants belong to the MADS box gene family. Since they are generally transcribed in those tissues and organs whose identity they determine, they are excellent markers for developmental processes. Here we report the cDNA cloning of a pair of MADS box genes, ZMM8 and ZMM14, from the monocotyledonous plant maize. Maize inflorescences are composed of spikelets which contain two florets, an upper and a lower one. Although upper and lower florets develop in a very similar way in male inflorescences, ZMM8 and ZMM14 expression was found in all organs of upper florets, but no transcripts were detected in lower florets. In contrast, two other MADS box genes were found to be expressed in lower florets in the same way as in upper florets. Our observations suggest that during spikelet development ZMM8 and ZMM14 work as selector genes which are involved in distinguishing the upper from the lower floret. Alternatively, these genes may be involved in conferring determinacy to the spikelet or upper floret meristem. Our data suggest that in the phylogenetic lineage that led to maize an ancient type of MADS box gene has been recruited during evolution for the establishment of novel positional information not found within the simple inflorescences of dicotyledonous plants such as Arabidopsis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004270050271
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  • 2
    Electronic Resource
    Electronic Resource
    Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth, mineral nutrient acquisition and root exudation of soil-grown maize plants (1995)
    Springer
    Mycorrhiza 5 (1995), S. 321-327 
    Details
    ISSN: 1432-1890
    Keywords: Glomus mosseae ; Zea mays ; Mineral uptake ; Root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-μm nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterle soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shoot∶root ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, threeto sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00207404
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  • 3
    Electronic Resource
    Electronic Resource
    Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth, mineral nutrient acquisition and root exudation of soil-grown maize plants (1995)
    Springer
    Mycorrhiza 5 (1995), S. 321-327 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus mosseae ; Zea mays ; Mineral uptake ; Root exudation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-μm nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterile soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shoot : root ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, three- to sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050079
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  • 4
    Electronic Resource
    Electronic Resource
    Manganese reduction in the rhizosphere of mycorrhizal and nonmycorrhizal maize (1994)
    Springer
    Mycorrhiza 5 (1994), S. 119-124 
    Details
    ISSN: 1432-1890
    Keywords: Glomus mosseae ; Manganese uptake ; Root exudation ; Manganese reduction ; Mycorrhizal effect ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of rhizosphere microorganisms and vesicular-arbuscular (VA) mycorrhiza on manganese (Mn) uptake in maize (Zea mays L. cv. Tau) plants was studied in pot experiments under controlled environmental conditions. The plants were grown for 7 weeks in sterilized calcareous soil in pots having separate compartments for growth of roots and of VA mycorrhizal fungal hyphae. The soil was left either uninoculated (control) or prior to planting was inoculated with rhizosphere microorganisms only (MO-VA) or with rhizosphere microorganisms together with a VA mycorrhizal fungus [Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe] (MO+VA). Mycorrhiza treatment did not affect shoot dry weight, but root dry weight was slightly inhibited in the MO+VA and MO-VA treatments compared with the uninoculated control. Concentrations of Mn in shoots decreased in the order MO-VA 〉 MO+VA 〉 control. In the rhizosphere soil, the total microbial population was higher in mycorrhizal (MO+VA) than nonmycorrhizal (MO-VA) treatments, but the proportion of Mn-reducing microbial populations was fivefold higher in the nonmycorrhizal treatment, suggesting substantial qualitative changes in rhizosphere microbial populations upon root infection with the mycorrhizal fungi. The most important microbial group taking part in the reduction of Mn was fluorescent Pseudomonas. Mycorrhizal treatment decreased not only the number of Mn reducers but also the release of Mn-solubilizing root exudates, which were collected by percolation from maize plants cultivated in plastic tubes filled with gravel quartz sand. Compared with mycorrhizal plants, the root exudates of nonmycorrhizal plants had two fold higher capacity for reduction of Mn. Therefore, changes in both rhizosphere microbial population and root exudation are probably responsible for the lower acquisition of Mn in mycorrhizal plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00202343
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  • 5
    Electronic Resource
    Electronic Resource
    Manganese reduction in the rhizosphere of mycorrhizal and nonmycorrhizal maize (1994)
    Springer
    Mycorrhiza 5 (1994), S. 119-124 
    Details
    ISSN: 1432-1890
    Keywords: Key words Glomus mosseae ; Manganese uptake ; Root exudation ; Manganese reduction ; Mycorrhizal effect ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of rhizosphere microorganisms and vesicular-arbuscular (VA) mycorrhiza on manganese (Mn) uptake in maize (Zea mays L. cv. Tau) plants was studied in pot experiments under controlled environmental conditions. The plants were grown for 7 weeks in sterilized calcareous soil in pots having separate compartments for growth of roots and of VA mycorrhizal fungal hyphae. The soil was left either uninoculated (control) or prior to planting was inoculated with rhizosphere microorganisms only (MO-VA) or with rhizosphere microorganisms together with a VA mycorrhizal fungus [Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe] (MO+VA). Mycorrhiza treatment did not affect shoot dry weight, but root dry weight was slightly inhibited in the MO+VA and MO-VA treatments compared with the uninoculated control. Concentrations of Mn in shoots decreased in the order MO-VA〉MO+VA〉control. In the rhizosphere soil, the total microbial population was higher in mycorrhizal (MO+VA) than nonmycorrhizal (MO-VA) treatments, but the proportion of Mn-reducing microbial populations was fivefold higher in the nonmycorrhizal treatment, suggesting substantial qualitative changes in rhizosphere microbial populations upon root infection with the mycorrhizal fungi. The most important microbial group taking part in the reduction of Mn was fluorescent Pseudomonas. Mycorrhizal treatment decreased not only the number of Mn reducers but also the release of Mn-solubilizing root exudates, which were collected by percolation from maize plants cultivated in plastic tubes filled with gravel quartz sand. Compared with mycorrhizal plants, the root exudates of nonmycorrhizal plants had two fold higher capacity for reduction of Mn. Therefore, changes in both rhizosphere microbial population and root exudation are probably responsible for the lower acquisition of Mn in mycorrhizal plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s005720050048
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  • 6
    Electronic Resource
    Electronic Resource
    Transport and dynamics of molecules dissolved in maize root cortex membranes (1995)
    Springer
    The journal of membrane biology 143 (1995), S. 19-28 
    Details
    ISSN: 1432-1424
    Keywords: Plant membrane ; Lipid domain ; Fluorescence photobleaching recovery ; Electron paramagnetic resonance ; Temperature stress ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Translational diffusion of a fluorescent sterol probe was measured in the plasma membranes of protoplasts isolated from cortical cells of the primary root of maize seedlings. The apparent lateral diffusion coefficient was typically observed to be nearly insensitive to temperature, while the mobile fraction increased with increasing temperature. These fluorescence photobleaching recovery (FPR) measurements were compared with the electron paramagnetic resonance (EPR) spectra of the methyl ester of 13-doxyl palmitic acid in membranes of corn root tissue in situ. The complex spectra observed with this probe were analyzed as weighted sums of simpler spectra of various order parameters and rotational correlation times. The reconstituted spectra calculated from the model show that EPR also detects a mobile (less ordered, fluid) fraction, distinguished by the order parameter S=0.1 to 0.2, which becomes more abundant as temperature increases and is qualitatively comparable to the mobile fraction determined by the FPR method. The observed results on the mobile fractions and the diffusion rates for translational (FPR) as well as rotational (EPR) motions are interpreted in terms of membrane organization, thus providing information on the population and structural patterns of the coexisting domains with a special emphasis on the response of the membrane to temperature changes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00232520
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  • 7
    Electronic Resource
    Electronic Resource
    Ca2+ pump and Ca2+/H+ antiporter in plasma membrane vesicles isolated by aqueous two-phase partitioning from corn leaves (1990)
    Springer
    The journal of membrane biology 114 (1990), S. 133-142 
    Details
    ISSN: 1432-1424
    Keywords: Ca2+ transport ; plasma membrane ; Ca2+ pump ; pH gradient ; Ca2+/H+ antiporter ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Plasma membrane vesicles, which are mostly right side-out, were isolated from corn leaves by aqueous two-phase partitioning method. Characteristics of Ca2+ transport were investigated after preparing inside-out vesicles by Triton X-100 treatment.45Ca2+ transport was assayed by membrane filtration technique. Results showed that Ca2+ transport into the plasma membrane vesicles was Mg-ATP dependent. The active Ca2+ transport system had a high affinity for Ca2+(K m (Ca2+)=0.4 μm) and ATP(K m (ATP)=3.9 μm), and showed pH optimum at 7.5. ATP-dependent Ca2+ uptake in the plasma membrane vesicles was stimulated in the presence of Cl− or NO 3 − . Quenching of quinacrine fluorescence showed that these anions also induced H+ transport into the vesicles. The Ca2+ uptake stimulated by Cl− was dependent on the activity of H+ transport into the vesicles. However, carbonylcyanidem-chlorophenylhydrazone (CCCP) and VO 4 3− which is known to inhibit the H+ pump associated with the plasma membrane, canceled almost all of the Cl−-stimulated Ca2+ uptake. Furthermore, artificially imposed pH gradient (acid inside) caused Ca2+ uptake into the vesicles. These results suggest that the Cl−-stimulated Ca2+ uptake is caused by the efflux of H+ from the vesicles by the operation of Ca2+/H+ antiport system in the plasma membrane. In Cl−-free medium, H+ transport into the vesicles scarcely occurred and the addition of CCCP caused only a slight inhibition of the active Ca2+ uptake into the vesicles. These results suggest that two Ca2+ transport systems are operating in the plasma membrane from corn leaves, i.e., one is an ATP-dependent active Ca2+ transport system (Ca2+ pump) and the other is a Ca2+/H+ antiport system. Little difference in characteristics of Ca2+ transport was observed between the plasma membranes isolated from etiolated and green corn leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01869094
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  • 8
    Electronic Resource
    Electronic Resource
    Nitrogen and phosphorus use in maize sole cropping and maize/cowpea mixed cropping systems on an Alfisol in the northern Guinea Savanna of Ghana (1991)
    Springer
    Biology and fertility of soils 10 (1991), S. 267-275 
    Details
    ISSN: 1432-0789
    Keywords: Vigna unguiculata ; Zea mays ; Nutrient competition ; Intercropping ; Nitrate depletion ; N2 fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The use of N and P by mixed and by sole cropping (crop rotation) of maize and cowpeas were compared in a field experiment on an Alfisol at the Nyankpala Agricultural Experiment Station in the northern Guinea Savanna of Ghana, using two levels of N (0 and 80 kg N ha-1 year-1 as urea) and P application (0 and 60 kg P ha-1 year-1 as Volta phosphate rock). Maize grain yields were significantly reduced in the mixed cropping system. This yield difference became smaller with the application of N and P fertilizer. The N and P concentrations in maize ear leaves at silking indicated that a deficiency in N and P contributed to the maize yield depression in mixed cropping. Competition for soil and fertilizer N between maize and cowpeas was suggested by: (1) A similarity in total N uptake between the two cropping systems; (2) efficient use of soil nitrate by the cowpeas; and (3) low N2 fixation by the cowpeas, calculated with the aid of an extended-difference method. In general, N2 fixation was low, with the highest values in the sole cropping (53 kg ha-1) and a substantial reduction in the mixed cropping system. The application of N fertilizer further reduced N2 fixation. This was substantiated by nodule counts. The lower N2 fixation in the mixed cropping system was only partly explained by the lower density of cowpeas in this system. In addition, dry spells during the cropping season and shading by the maize component could have reduced the nodulation efficiency. No N transfer from the legume/rhizobium to the non-legume crop was observed. Impaired P nutrition in the mixed compared with the sole-cropped maize might have been due to less P mobility in the soil. This was indicated by lower soil moisture contents in the topsoil under mixed cropping, especially during the dry year of 1986. The results show that mixed cropping of maize and cowpeas did not lead to improved use of soil and fertilizer N and P or to an enhanced N2 fixation. On the contrary, an annual rotation of maize and cowpeas was clearly superior.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337377
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  • 9
    Electronic Resource
    Electronic Resource
    Field evaluation of N2 fixation and N partitioning in climbing bean (Phaseolus vulgaris L.) using 15N (1992)
    Springer
    Biology and fertility of soils 13 (1992), S. 142-146 
    Details
    ISSN: 1432-0789
    Keywords: A value ; Common bean ; N remobilization ; Soil N balance ; Atom% 15N excess ; Phaseolus vulgaris ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The common bean (Phaseolus vulgaris L.) is generally regarded as a poor N2 fixer. This study assessed the sources of N (fertilizer, soil, and fixed N), N partitioning and mobilization, and soil N balance under field conditions in an indeterminate-type climbing bean (P. vulgaris L. cv. Cipro) at the vegetative, early pod-filling, and physiological maturity stages, using the A-value approach. This involved the application of 10 and 100 kg N ha-1 of 15N-labelled ammonium sulphate to the climbing bean and a reference crop, maize (Zea mays L.). At the late pod-filling stage (75 days after planting) the climbing bean had accumulated 119 kg N ha-1, 84% being derived from fixation, 16% from soil, and only 0.2% from the 15N fertilizer. N2 fixation was generally high at all stages of plant growth, but the maximum fixation (74% of the total N2 fixed) occurred during the interval between early (55 days after planting) and late podfilling. The N2 fixed between 55 and 75 days after planting bas a major source (88%) of the N demand of the developing pod, and only about 11% was contributed from the soil. There was essentially no mobilization of N from the shoots or roots for pod development. The cultivation of common bean cultivars that maintain a high N2-fixing capacity especially during pod filling, satisfying almost all the N needs of the developing pod and thus requiring little or no mobilization of N from the shoots for pod development, may lead to a net positive soil N balance.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336269
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  • 10
    Electronic Resource
    Electronic Resource
    Bioavailability of heavy metals and abundance of arbuscular mycorrhiza in a soil polluted by atmospheric deposition from a smelter (1995)
    Springer
    Biology and fertility of soils 19 (1995), S. 22-28 
    Details
    ISSN: 1432-0789
    Keywords: Arbuscular mycorrhiza ; Limed silty loam Heavy metals ; Pb-Zn smelter ; Root colonization Spore numbers ; Tolerance ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The bioavailability of heavy metals (Cd, Zn, Pb, Cu) and the abundance of arbuscular mycorrhiza (AM) were studied in two agricultural fields close to a Pb-Zn smelter and three fields outside the pollution zone all cultivated with maize (Zea mays L.). Metal extractability with ethylenediaminetetraacetic acid (EDTA)-NH4OAc and Ca(NO3)2, plant metal uptake, and mycorrhizal parameters (spore number, root colonization) were assessed at two growth stages (six-leaf and maturity). Despite regular liming, the availability of Cd, Zn, and Pb was markedly higher in the two metal-polluted fields than in the three uncontaminated fields. However, the AM abundance was not correlated with metal availability. Root colonization and spore numbers in the metal polluted fields were relatively high, though at plant maturity the former was significantly lower than in one of the uncontaminated fields. The very low AM abundance in the two other unpolluted fields was related to other factors, particular soil and plant P status and soil pH. AM root colonization did not substantially prevent plant metal accumulation, since the metal concentrations in maize grown on the polluted fields strongly exceeded normal values, and for Cd and Pb reached the limits of toxicity for animal feed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336342
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  • 11
    Electronic Resource
    Electronic Resource
    Interaction between Alternaria alternata or Fusarium equiseti and Glomus mosseae and its effects on plant growth (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 301-305 
    Details
    ISSN: 1432-0789
    Keywords: Key wordsAlternaria alternata ; Arbuscular mycorrhizas ; Fusarium equiseti ; Glomus mosseae ; Lactuca sativa ; Lettuce ; Maize ; Saprophytic fungi ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of inoculation with the saprophytic fungi Alternaria alternata or Fusarium equiseti on maize (Zea mays) and lettuce (Lactuca sativa) with or without arbuscular mycorrhizal (AM) colonization by Glomus mosseae was studied in a greenhouse trial. Plant dry weights of non-AM-inoculated maize and lettuce were unaffected by the presence of A. alternata and F. equiseti. In contrast, A. alternata and F. equiseti decreased plant dry weights and mycorrhization when inoculated to the rhizosphere before G. mosseae. The saprophytic fungi inoculated 2 weeks after G. mosseae did not affect the percentage of root length colonized by the AM endophyte, but did affect its metabolic activity assessed as succinate dehydrogenase activity. Although F. equiseti inoculated at the same time as G. mosseae did not affect mycorrhization of maize roots, its effect on AM colonization of lettuce roots was similar to that with A. alternata. In the rhizosphere of both plants, the population of saprophytic fungi decreased significantly, but was not affected by the presence of G. mosseae. Our results suggest that there may have been a direct effect of the saprophytic fungi on the mycorrhizal fungi in the extramatrical phase of the latter, and when the AM fungus was established in the root the AM fungus was less affected by the saprophytic fungi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003740050247
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  • 12
    Electronic Resource
    Electronic Resource
    Fitting plants to soil through mycorrhizal fungi: plant nutrition in host-endophyte combinations evaluated by the diagnosis and recommendation integrated system (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 96-102 
    Details
    ISSN: 1432-0789
    Keywords: DRIS ; Helianthus annus ; Plant nutrition ; VAM ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Vesicular-arbuscular mycorrhizal (VAM) fungi improve plant growth in marginal soils. This study was conducted to determine the effects of three species of VAM fungi on plant nutrition in two cultivars of corn (Zea mays L.) and one of sunflower (Helianthus annus L.). Plants were grown in pot cultures under controlled (greenhouse) conditions in a soil high in K, Mg, and P, and low in Ca and N, and were supplied with amounts of VAM-fungal inocula in which equal numbers of infective propagules had previously been determined. Analysis of variance showed highly significant main effects and interactions due to both factors (plant and fungus) for N, P, Ca, and Mg. For K, only plant effects were significant (P〈0.043). The uptake of nutrients was selectively enhanced or inhibited by one or the other VAM fungus relative to non-VAM control plants. In sunflower, N concentration was markedly enhanced (73%) by the mixed inoculum of the three fungi, even though individual effects were not significant. Evaluation of leaf nutrient analyses by the Diagnosis and Recommendation Integrated System (DRIS) revealed the utility of this system to rank nutritional effects by VAM fungi in an order of relative nutrient deficiency. The DRIS therefore is seen as a useful tool in evaluating and selecting VAM fungi for the alleviation of specific nutrient disorders.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00336425
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  • 13
    Electronic Resource
    Electronic Resource
    Mineralization of nitrogen in fertilizer-acidified lime-amended soils (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 249-252 
    Details
    ISSN: 1432-0789
    Keywords: N fertilizer requirement ; Nitrification ; Zea mays ; N mineralization ; Lime ; Soil pH ; Nitrate-N
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The application of NH inf4 su+ -based fertilizers to soils slowly lowers soil pH, which in turn decreases nitrification rates. Under these conditions nitrification and N mineralization may be reduced. We therefore investigated the impact of liming fertilizer-acidified soils on nitrification and N mineralization. Soil samples were collected in the spring of 1987 from a field experiment, initiated in 1980, investigating N, tillage, and residue management under continuous corn (Zea mays L.). The pH values (CaCl2) in the surface soil originally ranged from 6.0 to 6.5. After 6 years the N fertilizer and tillage treatments had reduced the soil pH to values that ranged between 3.7 and 6.2. Incubation treatments included two liming rates (unlimed or SMP-determined lime requirement), two 15N-labeled fertilizer rates (0 or 20 g N m-2), and three replicates. Field-moist soil was mixed with lime and packed by original depth into columns. Labeled-15N ammonium sulfate in solution was surface-applied and columns were leached with 1.5 pore volumes of deionized water every 7 days over a 70-day period. Nitrification occurred in all pH treatments, suggesting that a ferilizer-acidified soil must contain a low-pH tolerant nitrifier population. Liming increased soil pH values (CaCl2) from 3.7 to 6.2, and increased by 10% (1.5 g N m-2) the amount of soil-derived NO3 --N that moved through the columns. This increase was the result of enhanced movement of soil-derived NO3 --N through the columns during the first 14 days of incubation. After the initial 14-day period, the limed and unlimed treatments had similar amounts of soil N leaching through the soil columns. Lime increased the nitrification rates and stimulated the early movement of fertilizer-derived NO3 --N through the soil.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00337208
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  • 14
    Electronic Resource
    Electronic Resource
    Influence of management practices on soil organic matter, microbial biomass and cotton yield in Alabama‘s ’’Old Rotation’ (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 353-358 
    Details
    ISSN: 1432-0789
    Keywords: Key words Soil carbon ; Crop rotation ; Legumes ; Cover crop ; Nitrogen fertilization ; Microbial biomass ; Soil health ; Gossypium hirsutum ; Zea mays ; Trifolium ; incarnatum ; Glycine max
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The “Old Rotation” cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha–1 year–1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha–1 year–1 as NH4NO3; and III, 3-year cotton-corn- (alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134g N as NH4NO3 ha–1 year–1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha–1 year–1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha–1 year–1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r 2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r 2=0.87 and 0.98, respectively). After 99 years of management the “Old Rotation” cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.
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    URL: http://dx.doi.org/10.1007/s003740050182
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  • 15
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    Effects of green manure and coral lime on corn growth and chemical properties of an acid Oxisol in Western Samoa (1997)
    Springer
    Biology and fertility of soils 24 (1997), S. 266-273 
    Details
    ISSN: 1432-0789
    Keywords: Key words Green manure ; Lime ; K deficiency ; Oxisol ; Sweet corn ; Zea mays ; Mn toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Effects of local green manure (GM) and lime on soil productivity in a low-input agricultural system were evaluated by growing three successive crops of sweet corn (Zea mays) on an acid Oxisol (Typic acrorthox, Togitogiga series) in Western Samoa. The soil was amended with coral lime at 0, 5, and 10Mgha–1 and with cowpea GM at 0, 7.5, and 15Mgha–1. Commercial NPK fertilizers at 50kgha–1 each of N, P, and K were included for comparison. The amendments were applied only once prior to planting of the first crop. Response parameters measured included nutrient composition of leaves at tasseling and grain yield of each crop, and selected soil chemical properties at each planting. Yields of the first crop were nearly tripled with GM additions and doubled with lime additions. Such yield increases were caused mainly by better K nutrition and to a lesser extent by enhanced P nutrition. Yields of subsequent crops were much lower than those of the first, and the declines were much steeper for the GM treatments than for the lime treatments. Thus, the enhancement effect on K nutrition did not last beyond one crop. Poor growth of the second and third crops was caused by K deficiency; probably coupled with Mn toxicity. Significant yield reductions were found when Mn-to-K ratios in leaves exceeded 0.010. As for effects on soil, soil pH was increased significantly by lime but only slightly by GM. Given the variable charge property of this Oxisol, each unit pH increase corresponds to a cation exchange capacity (CEC) increase of 5cmolckg–1. Having greater CEC, the amended soil retained K more effectively, thereby causing yield increases, especially of the first corn crop, which required at least 0.75cmolckg–1 of exchangeable soil K or 7% of CEC for adequate growth.
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    URL: http://dx.doi.org/10.1007/s003740050242
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  • 16
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    Relationship of soil carbon light fraction, microbial activity, humic acid production and nitrogen fertilization in the decaying process of corn stubble (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 75-78 
    Details
    ISSN: 1432-0789
    Keywords: Key words Corn stubble decomposition ; N-fertilization ; Carbon light fraction ; Humic acids ; Microbial activity ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The variation in stubble decomposition due to fertilizer incorporation was determined in a typical Argiudoll of the Argentinian rolling pampas. The experiment was conducted for 15 years, which included a no till system under maize (Zea mays L.) and a soybean rotation (Glycine max) with 0 and 45kg N ha–1 nitrogen fertilization treatments, called NFS and FS, respectively. A higher proportion of residues with a high N content was found in the FS plots. The different substrate quality proved to be the regulating factor for mineralization. This activity was indicated by the increase in soil microbial activity and soil carbon light fraction in FS compared to NFS. This carbon light fraction mineralizes rapidly but does not contribute to the most stable components, which are related to synthesis and polymerization of humic acids. No significant differences in humic acid content were found.
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    URL: http://dx.doi.org/10.1007/s003740050283
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  • 17
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    Influence of tillage system on denitrification in maize-cropped soils (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 142-146 
    Details
    ISSN: 1432-0789
    Keywords: Key words Denitrification ; Tillage systems ; Maize ; Zea mays ; Hot spots ; Denitrifying populations ; N2O emission
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Denitrification losses show an irregular pattern through the year, often being caused by climatic conditions and management practices. The objectives of the present work were to quantify denitrification losses and to determine the influence of tillage system on the factors that control denitrification in fertilized soils. The modal profile of the soil was an Vertic Argiudoll, clay loam texture, located in Buenos Aires province, Argentina. The treatments were: (a) fertilized, (b) incorporated fertilization and (c) without fertilization for both no tillage and conventional tillage systems. Chambers were placed in the field to measure denitrification. In this clayish soil the estimated mean values of accumulated denitrification during the crop cycle (90 days) were 0.190kgNha–1 for conventional tillage and 0.350kgNha–1 for no tillage. In treatments with no tillage, losses by denitrification were approximately twice those of conventional tillage. These differences were also evidenced by the number of microorganisms, which were significantly higher (P〈〉;5%) for no tillage on all dates, except for at flowering. The increase at flowering coincided with the period of highest rainfall and consequently the highest water contents in the soil. The highest denitrification losses, except for sowing, were measured when soil moisture content was more than 30% (v/v). Denitrification increased in conjunction with an increase in the availability of carbon that is consumed by the heterotrophic microorganisms (including the denitrifiers).
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    URL: http://dx.doi.org/10.1007/s003740050294
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  • 18
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    Growth and nitrogen nutrition of maize (Zea mays L.) in soil treated with the nitrification-inhibiting insecticide Baythroid (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 161-165 
    Details
    ISSN: 1432-0789
    Keywords: Key words ANI ; Baythroid ; Cyfluthrin ; Insecticide ; 15N ; Nitrification ; N uptake ; Synthetic pyrethroid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the uptake and dry matter production potential of NH+ 4 and NO– 3 and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO– 3 was significantly higher than that of NH+ 4 when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH+ 4 showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH+ 4 due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation.
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    URL: http://dx.doi.org/10.1007/BF00336057
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  • 19
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    Influence of management practices on soil organic matter, microbial biomass and cotton yield in Alabama's “Old Rotation” (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 353-358 
    Details
    ISSN: 1432-0789
    Keywords: Soil carbon ; Crop rotation ; Legumes ; Cover crop ; Nitrogen fertilization ; Microbial biomass ; Soil health ; Gossypium hirsutum ; Zea mays ; Trifolium incarnatum ; Glycine max
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The “Old Rotation” cotton experiment was designed to aid farm managers in implementing rotation schemes that not only increase yield, but also improve soil quality. Six different crop rotation treatments were imposed since 1896. Rotations were: IA, cotton (Gossypium hirsutum L.) grown every year without a winter legume and without N fertilization; IB, cotton grown every year with a winter legume and without N fertilization; IC, cotton grown every year without a winter legume and with 134 kg N as NH4NO3 ha-1 year-1; IIA, 2-year cotton-corn (Zea mays L.) rotation with a winter legume and without N fertilization; IIB, 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 as NH4NO3; and III, 3-year cotton-corn- alternating soybean [Glycine max (L.) Merr.] or rye (Secale cereale L.) rotation with a winter legume and with 134 g N as NH4NO3 ha-1 year-1. Crimson clover (Trifolium incarnatum L.) was the winter legume cover crop. The 2-year cotton-corn rotation with a winter legume and with 134 kg N ha-1 year-1 (IIB) and the 3-year cotton-corn soybean/rye rotation with a winter legume and with 134 kg N ha-1 year-1 (III) had higher amounts of soil organic matter, soil microbial biomass C and crop yield than the other four treatments. The cotton grown every year without a winter legume or N fertilizer (IA) had a lower amount of soil organic matter, soil microbial biomass C and N and cotton seed yield than all other rotations. In 1988 and 1992 cotton seed and legume yield were correlated in positive, curvilinear relationships with soil organic matter (r 2 ranged from 0.72 to 0.87). In most months, soil microbial biomass C and N was lower in the cotton grown every year without winter legumes or fertilizer (IA) than the other five rotations. In 1994, microbial biomass C and the Cmic:Corg ratio correlated in positive, curvilinear relationships with seed cotton yield (r 2=0.87 and 0.98, respectively). After 99 years of management the “Old Rotation” cotton experiment indicates that winter legumes increase amounts of both C and N in soil, which ultimately contribute to higher cotton yields. Microbial biomass C and the Cmic:Corg ratio are poor predictors of annual crop yield but may be an accurate indicator of soil health and a good predictor of long-term crop yield.
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    URL: http://dx.doi.org/10.1007/BF00335906
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  • 20
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    Pleiotropic effects of a nuclear restorer-of-fertility locus on mitochondrial transcripts in male-fertile and S male-sterile maize (1999)
    Springer
    Current genetics 35 (1999), S. 521-526 
    Details
    ISSN: 1432-0983
    Keywords: Key words Cytoplasmic male sterility ; Fertility restoration ; Zea mays ; Mitochondrial transcripts
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytoplasmic male sterility (CMS) is encoded by the plant mitochondrial genome and can be reversed by nuclear restorer-of-fertility(Rf) alleles. In the CMS-S system of maize, reproductive failure and fertility restoration are gametophytic, occurring during the starch-filling stages of pollen development. Transcripts of the CMS-S-associated mitochondrial open reading frames (orf355 and orf77) are present from the early stages of microspore development through the aborted pollen stage. To investigate the molecular basis of fertility restoration, we compared mitochondrial-transcript accumulation in aborting CMS-S pollen and in CMS-S pollen restored to fertility by the Rf3 nuclear allele. In the presence of the Rf3 allele, novel, shorter transcripts of the orf355-orf77, cob and atp6 mitochondrial genes were created, and the relative abundance of larger transcripts was decreased for each of these loci. The altered transcript patterns cosegregated with male fertility conditioned by the Rf3 allele. The novel cob and atp6 transcripts were also observed in leaf-tissues of both normal and S-cytoplasm plants carrying the Rf3 allele. These observations support the hypothesis that the Rf3 allele encodes, or regulates, a modifier of mitochondrial transcript (Mmt) activity that affects both CMS and essential mitochondrial gene transcripts.
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    URL: http://dx.doi.org/10.1007/s002940050448
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  • 21
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    The response of maize (Zea mays) to Azospirillum inoculation in various types of soils in the field (1996)
    Springer
    World journal of microbiology and biotechnology 12 (1996), S. 511-515 
    Details
    ISSN: 1573-0972
    Keywords: Azospirillum ; Plant growth promotion ; Rhizosphere ; inoculants ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Application of a peat-based powder inoculant of Azospirillum brasilense, as well as a granular inoculant (each containing 0.5–1.0×107 Azospirillum/g moist peat), in the seed furrows of Zea mays resulted in significantly increased yields (11 to 14%) in light soils at low rates of N fertilization. In general, there was no effect of inoculation on plant yields in heavier soils nor when N fertilization was high. Pre-emergence application of granular inoculant and inoculation associated with irrigation were more efficient in increasing yield than inoculation post-emergence or seed coating.
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    URL: http://dx.doi.org/10.1007/BF00419465
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  • 22
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    Effect of aflatoxin B1 on chlorophyll, nucleic acid and protein contents in maize (1997)
    Springer
    Biologia plantarum 39 (1997), S. 47-50 
    Details
    ISSN: 1573-8264
    Keywords: carotenoids ; DNA ; RNA ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Aflatoxin B1 significantly lowered the contents of nucleic acids (DNA, RNA) and protein (both quantititive and qualitative) of germinating seeds of maize cv. Suwan Composite and also the contents of chlorophylls and carotenoids in seedlings. The extent of inhibition depended on the concentration of toxin.
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    URL: http://dx.doi.org/10.1023/A:1000352821598
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  • 23
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    Somatic embryogenesis of maize hybrids: histological analysis (1997)
    Springer
    Biologia plantarum 39 (1997), S. 431-436 
    Details
    ISSN: 1573-8264
    Keywords: morphogenesis ; plumule ; polyembryos ; radicle ; scuttellum ; Zea mays ; zygotic embryos
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The immature zygotic embryos of reciprocal maize hybrids (CHI-31 x GF1 and CHI-31 × GE2) were used as the initial material for induction of somatic embryogenesis in vitro. Histological analysis of somatic embryogenesis revealed high developmental variability. The arising formations were classified into 5 groups: A) somatic embryos phenotypically similar to zygotic embryos, B) polyembryos, C) formations with radicle but without meristematic plumule, D) formations with radicle without differentiated plumule, and E) formations with plumule without radicle. The formatioms A and B regenerated directly into plants. Plant regeneration from formations E required preculture on the rooting medium. Formations C and D failed to develope into plants possibly because of early loss of meristematic cell character during the embryo axis differentiation. The reverse sequence of radicle and plumule differentiation in somatic embryos in comparison with zygotic ones was noted. The epigenetic character of the scutellum, coleoptile, coleorhiza and leaves primordia development was discussed.
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    URL: http://dx.doi.org/10.1023/A:1001044613230
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  • 24
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    Nitrate reductase activity and uptake of nitrate and oxygen as affected by nitrate supply to detached maize organs (1997)
    Springer
    Biologia plantarum 39 (1997), S. 583-589 
    Details
    ISSN: 1573-8264
    Keywords: dissimilatory NR ; substrate induction ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Supply of 1, 2, 5, 10 or 20 mM nitrate to detached roots, scutella or shoots from 5- to 6-d-old Zea mays L. seedlings increased in vitro nitrate reductase (NR) activity in all the organs and NADPH specific NR (NADPH:NR) activity in roots and scutella but not in the shoots. Usually 2 to 5 mM nitrate supported maximum enzyme activity, the higher concentration did not increase it further. The protein content in the roots, scutella and shoots increased up to 5, 2 and 20 mM medium nitrate, respectively. Nitrate uptake also increased with increasing nitrate concentration in roots and shoots, but it increased only slightly in the scutella. In both roots and scutella, methionine sulfoximine had no effect, while cycloheximide and tungstate abolished nitrate induced NADH:NR activity completely and NADPH:NR partially. Methionine sulfoximine increased nitrate uptake by roots and scutella slightly, but other inhibitors had no effect. The depletion of dissolved oxygen from the medium was lower in the presence of nitrate than in its absence or in the presence of ammonium, especially in the scutella.
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    URL: http://dx.doi.org/10.1023/A:1000982832369
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  • 25
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    Longitudinal component of trans-root electrical potential difference: evidence from application of metabolic inhibitors to the cut end of excised maize roots (1997)
    Springer
    Biologia plantarum 40 (1997), S. 203-209 
    Details
    ISSN: 1573-8264
    Keywords: ATPase ; plasma membrane redox pump ; proton gradient ; respiration ; saccharose ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in trans-root electrical potential induced by application of metabolic inhibitors (carbonyl cyanide m-chlorophenylhydrazone, vanadate, diethylstilbestrol, N-ethyl maleimide, p-chloromercuribenzene sulfonic acid, KCN, salicylhydroxamic acid) and electron acceptors (hexachloroiridate IV and hexacyanoferrate III) to the cut end of excised roots of maize demonstrated existence of a longitudinal component of trans-root electrical potential. It was probably associated with redox plasma membrane bound system(s) and coupled to the cyanide sensitive and alternative respiration pathways.
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    URL: http://dx.doi.org/10.1023/A:1001060301961
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  • 26
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    Non-destructive stereological method for estimating the length of rigid root systems (1997)
    Springer
    Biologia plantarum 40 (1997), S. 311-316 
    Details
    ISSN: 1573-8264
    Keywords: growth analysis ; total vertical projections ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A non-destructive method of total vertical projections for estimating the length of rigid root systems, not introduced yet in plant sciences, is described. It is demonstrated on measuring less and more dense root systems of seedlings of Zea mays grown at hypoxic or control conditions. Photographs of six vertical projections (30° apart) of each root system were taken and evaluated. The method being based on proved mathematical formula offers unbiased estimation of the length of a rigid root system, curved in three-dimensional space, by non-destructive means. Thus, it is applicable during ongoing experimentation on plants grown in a solution culture. It was shown that less than 120 intersections between the root projection and test lines in one photograph ensured sufficient precision of the method and that the observer subjectivity could be overcome by presented instructions.
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    URL: http://dx.doi.org/10.1023/A:1001063725159
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  • 27
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    The isomerization of glutamate dehydrogenase in response to lead toxicity in maize (1997)
    Springer
    Biologia plantarum 40 (1997), S. 389-398 
    Details
    ISSN: 1573-8264
    Keywords: amination reaction ; glutathione ; oxidative stress ; suppressed GDH isoenzymes ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays) was cultivated on lead-adultrated soil up to 600 mg(Pb) kg-1. At maturity, the maize seeds were harvested. The glutamate dehydrogenase (GDH) was fractionated to its isoenzyme population by Rotofor isoelectric focusing (IEF). The increasing Pb concentration progressively enhanced the more acidic isoenzymes (pI 6.3 - 6.5), and at the same time suppressed the less acidic isoenzymes (pI 7.3 - 7.8) and at the 600 mg(Pb) kg-1(soil) only the most acidic couple of isoenzymes (pI 6.3, and 6.5) were detectable. The NH4+ Km values of the GDH increased progressively from 6.2 in the control to 100 mM and the total glutathione content of maize seeds from 60 to 240 nmol g-1 in the 600 mg(Pb) kg-1(soil) treated maize. The orderly, and sequential isomerization of GDH in response to Pb suggests that the enzyme functions as a sensor in the monitoring of environmentally induced stress.
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    URL: http://dx.doi.org/10.1023/A:1001018014681
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  • 28
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    Combined effects of aflatoxin B1 and citrinin on maize seedlings (1997)
    Springer
    Biologia plantarum 40 (1997), S. 441-447 
    Details
    ISSN: 1573-8264
    Keywords: α-amylase ; carotenoids ; chlorophyll ; DNA ; RNA ; starch ; sugars ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effect of two important mycotoxins, aflatoxin B1 and citrinin (concentration 2 g m-3) at various combinations (i.e., 1:1, 1:2, 2:1, 1:3 and 3:1, v/v) on seed germination, seedling growth, chlorophyll, carotenoid, starch, sugar, protein and nucleic acid contents, α-amylase activity, and respiration quotient was studied in maize cv. Suwan composite. The maximum and minimum inhibitions were recorded in most of the above parameters (except starch) at 3:1 and 1:3 combination ratios of these toxins, respectively. However, the inhibition rates varied with the treatments.
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    URL: http://dx.doi.org/10.1023/A:1001182401477
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  • 29
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    Impacts of Boron Application on Maize Plants Growing under Flooded and Unflooded Conditions (1998)
    Springer
    Biologia plantarum 41 (1998), S. 101-109 
    Details
    ISSN: 1573-8264
    Keywords: chlorophyll ; leaf relative water content ; membrane stability ; waterlogging ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants of maize (Zea mays L.) were waterlogged for 7 d and irrigated (root application) or sprayed (foliar application) with 0, 1, 3 and 6 mg dm-3 of boron. The stability of leaf membranes was assessed by determining leakage of electrolytes from leaf discs exposed to heat (51 °C) and dehydration (40 % PEG). Leaf membranes were more stable to heat than to dehydration. The membranes of waterlogged plants were more injured than those of control plants. Waterlogging reduced contents of dry mass, chlorophyll, soluble proteins, total free amino acids and soluble sugars and leaf relative water content (RWC). Application of boron increased the stability of leaf membranes, chlorophyll, soluble sugars, soluble proteins, amino acids contents, leaf RWC and dry mass accumulation. Foliar boron application was more effective. Application of boron alleviated the deleterious effect of waterlogging.
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    URL: http://dx.doi.org/10.1023/A:1001720702268
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    Relationship between development of endosperm transfer cells and grain mass in maize (1998)
    Springer
    Biologia plantarum 41 (1998), S. 539-546 
    Details
    ISSN: 1573-8264
    Keywords: cytoplasm ; endoplasmatic reticulum ; ingrowth ; mitochondria ; nuclei ; vesicles ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The most basal endosperm cells of maize (Zea mays L.) began differentiating into transfer cells in 10 days after pollination (DAP). The thickening and ingrowths forming in the transfer cell wall were slow during 10 and 15 DAP. There were many vesicles, silky and string ball objects in cytoplasm, and the number of mitochondria and rough endoplasm reticulum increased. After 15 DAP, the wall thickening and ingrowths forming in the transfer cells sped up. By 20 DAP, the transfer cell zone had developed, there appeared 65 - 70 rows of cells in width and 3 - 4 layers of cell in depth, the obvious cell wall ingrowths presented strong positive reaction with periodic acid Schiff's reagent. After 20 DAP, no significant change appeared in the shape and structure of the transfer cells, and the transfer cells entered function stage. In the mature kernels (53 DAP), the most basal transfer cells were filled with ingrowths, however, dense cytoplasm was also found in these cells. The nuclei had quite irregular shapes in these cells. Some transfer cells contained black grains and crystals. A black layer formed in the pericarp tissue adjacent to the transfer cell zone. Full development of endosperm transfer cells was important for reduction of kernel abortion and increase of kernel mass.
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    URL: http://dx.doi.org/10.1023/A:1001840316163
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    Effect of Potassium, and Abscisic and Indole-3-Acetic Acids, on Maize Root Xylem Exudation and Potassium Efflux (1999)
    Springer
    Biologia plantarum 42 (1999), S. 137-141 
    Details
    ISSN: 1573-8264
    Keywords: potassium recycling ; water uptake ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The influence of potassium sulfate, abscisic acid (ABA) and indole-3-acetic acid (IAA) solutions on xylem exudation rate and potassium efflux from the apical cut end of root tips of intact maize (Zea mays L. cv. Dnepropetrovskaya) seedlings was studied. Foliar application of 5 mM K2SO4 considerably stimulated the exudation rate. The application of ABA and IAA (1 mM) also induced a high rate of xylem exudation, K+ efflux being simultaneously increased.
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    URL: http://dx.doi.org/10.1023/A:1002137408222
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    The effect of selected plant hormones on in vitro proliferation of hyphae of Glomus fistulosum (1998)
    Springer
    Biologia plantarum 41 (1998), S. 255-263 
    Details
    ISSN: 1573-8264
    Keywords: abscisic acid ; N6-benzyladenosine ; gibberellic acid ; indole-3-acetic acid ; indole-3-butyric acid ; jasmonic acid ; kinetin riboside maize ; Zea mays ; zeatin riboside
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of N6-benzyladenine, kinetin, zeatin, N6-benzyladenosine, kinetin riboside, zeatin riboside, jasmonic acid, indole-3-acetic acid, indole-3-butyric acid, indole-3-propionic acid, abscisic acid and gibberellic acid on proliferation of hyphae of arbuscular mycorrhizal (AM) fungus Glomus fistulosum were studied under axenic conditions in vitro. The growth of intraradical hyphae of G. fistulosum was fully suppressed by 30 µM indole-3-acetic acid, but a perceptible decrease in the proliferation of the hyphae was observed already at 3 µM. Because such concentration is near the concentrations common in root tissues in vivo, the effect may be biologically significant. Similar effect was also observed for Glomus mosseae. Inhibitory effects of abscisic acid and cytokinins occurred only at very high, non-physiological concentrations. Ribosylated cytokinins showed stronger inhibition effects than their non-ribosylated counterparts. No stimulation of proliferation of hyphae by any plant hormone tested was observed.
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    Effect of flavonoids on in-vitro proliferation of hyphae of Glomus fistulosum (1998)
    Springer
    Biologia plantarum 41 (1998), S. 303-306 
    Details
    ISSN: 1573-8264
    Keywords: biochanin A ; luteolin ; maize ; naringenin ; quercetin ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Biochanin A, luteolin, naringenin and quercetin significantly decreased the percentage of root segments bearing the intraradical proliferating hyphae of Glomus fistulosum at the concentrations up to 10 µmol dm-3. The growth of hyphae was inhibited by biochanin A and luteolin whereas no significant effects of quercetin and naringenin were observed.
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    URL: http://dx.doi.org/10.1023/A:1001807823100
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    The effect of local application of fertilizer on the content of cytokinins in the xylem sap of maize (1998)
    Springer
    Biologia plantarum 41 (1998), S. 587-590 
    Details
    ISSN: 1573-8264
    Keywords: immunoassay ; root exudation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Cytokinin content in xylem sap was higher in plants grown under local supply of fertilizers as compared to those grown under homogenous distribution of nutrients in soil. The separate assay of cytokinins in xylem exudate from split root system showed that roots, which were in contact with fertilizer mainly contributed to cytokinins transported from roots to shoots.
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    URL: http://dx.doi.org/10.1023/A:1001800702050
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    Response of Three Arbuscular Mycorrhizal Fungi to Simulated Acid Rain and Aluminium Stress (1999)
    Springer
    Biologia plantarum 42 (1999), S. 289-296 
    Details
    ISSN: 1573-8264
    Keywords: Acaulospora tuberculata ; alkaline phosphatase ; Deschampsia flexuosa ; extraradical mycelium ; Glomus fistulosum ; Glomus mosseae ; maize ; NADH-diaphorase ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Simulated acid rain (SAR) combined with higher concentration of aluminium (SAR+Al) influenced the ecophysiology of three arbuscular mycorrhizal fungi (AMF) in both the germination and symbiotic phases of their life cycle. Acaulospora tuberculata, an isolate from the soil with low pH, exhibited a higher tolerance to environmental stress as compared to Glomus mosseae and G. fistulosum. This higher tolerance may be related to the edaphic conditions of soil of the isolate origin. The histochemical staining of the alkaline phosphatase and NADH-diaphorase activities in the extraradical mycelium (ERM) of the AMF proved to be more sensitive indication of negative effects of the SAR or SAR+Al stress compared to commonly measured parameters of the AMF such as mycorrhizal colonisation or growth of the ERM.
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    URL: http://dx.doi.org/10.1023/A:1002125005497
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    Fitting plants to soil through mycorrhizal fungi: Mycorrhiza effects on plant growth and soil organic matter (1993)
    Springer
    Biology and fertility of soils 15 (1993), S. 103-106 
    Details
    ISSN: 1432-0789
    Keywords: Helianthus annuus ; Mycorrhiza ; Soil organic matter ; VAM response ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Vesicular-arbuscular mycorrhizal (VAM) fungi affect diverse aspects of plant form and function. Since mycorrhiza-mediated changes in host-plant responses to root colonization by different VAM fungi vary widely, it is important to assess each endophyte for each specific effect it can elicit from its host as part of the screening process for effectiveness. Three species of VAM fungi and a mixture of species were compared with non-VAM controls for their effects on soil organic matter contents and on nutrition and morphology in two varieties (native and hybrid) of corn (Zea mays L.) and one of sunflower (Helianthus annuus L.) in P-sufficient and N-deficient soil in pot cultures. Differences in soil organic matter due to the fungal applications were highly significant with all host plants. Native corn responded more to VAM colonization than the hybrid did; differences in treatments were significant in leaf area, plant biomass, and root: shoot ratio in the former, but not in the latter. Responses in the sunflower were similar to those in the native corn. Significant VAM treatment-related differences in shoot N and P contents were not reflected in shoot biomass, which was invariant. Correlations between plant or soil parameters and the intensity of VAM colonization were found only in soil organic matter with the native corn, in specific leaf area in the hybrid corn, and in plant biomass in the sunflower. The presence of the different endophytes and not the intensity of colonization apparently elicited different host responses.
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    Ammonium-excreting Azospirillum sp. become intracellularly established in maize (Zea mays) para-nodules (1994)
    Springer
    Biology and fertility of soils 17 (1994), S. 1-8 
    Details
    ISSN: 1432-0789
    Keywords: Ammonium excretion ; Azospirillum brasilense ; Auxine ; 2,4-Dichlor-phenoxy-acetic acid ; Nitrogen fixation ; Paranodulation ; Maize ; Zea mays ; Electron microscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Maize seedlings develop nodule-like tumour knots (para-nodules) along primary roots when treated with the auxin 2,4-dichlor-phenoxy-acetic acid (2,4-D). Inoculated NH 4 + -excreting Azospirillum brasilense cells were shown to colonize these tumours, mostly intracellularly, promoting a high level of N2 fixation when microaerophilic conditions were imposed. The nitrogenase activity inside the para-nodules was less sensitive to free O2 than in non-para-nodulating roots. Both light and electron microscopy showed a dense bacterial population inside intact tumour cells, with the major part of the cell infection along a central tumour tissue. The bacteria colonized the cytoplasm with a close attachment to inner cell membranes. In an auxin-free growth medium, young 2,4-D-induced para-nodules grew further to become mature differentiated root organs in which introduced bacteria survived with a stable population. These results provide evidence that gramineous plants are potentially able to create a symbiosis with diazotrophic bacteria in which the NH 4 + -excreting symbiont will colonize para-nodule tissue intracellularly, thus becoming well protected.
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    Efficacy of root litter as a biofertiliser (1994)
    Springer
    Biology and fertility of soils 18 (1994), S. 228-230 
    Details
    ISSN: 1432-0789
    Keywords: Fine root ; Root litter ; Biofertiliser ; Leucaena leucocephala ; Trigonella foenum-graecum ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The efficacy ofLeucaena leucocephala root litter as a natural biological fertiliser was assessed usingZea mays as a test plant. Up to 8% of the fine roots of the plants constituted root litter. This fine root litter was better than that ofTrigonella foenum-graecum at increasing the growth and productivity ofZea mays. The root litter increased the growth of maize shoots more than the growth of roots. This appears to be a general phenomenon when plant nutrients are insufficient, as in the present study.
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    Nitrogen use in maize-grain legume cropping systems in semi-arid Kenya (1995)
    Springer
    Biology and fertility of soils 20 (1995), S. 57-62 
    Details
    ISSN: 1432-0789
    Keywords: Nitrogen use ; Nitrogen fertilizer recovery ; Zea mays ; Phaseolus vulgaris ; Vigna unguiculata ; Nitrogen fixation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Locally suitable cultivars of maize, beans, and cowpeas were grown in field experiments for four seasons in semi-arid Kenya. For three seasons, the dry matter production and grain yield of maize and beans were not increased by N fertilizer additions up to 120 kg N ha-1. Fertilizer recoveries measured by 15N isotope dilution techniques were low, less than 20%. Inoculated and uninoculated beans failed to fix N2. By contrast the cowpea derived 50% of its N from fixation, equivalent to 197 kg N ha-1. The N content of the grain generally exceeded 40 kg N ha-1, and the N content of the seeds from the grain legumes were greater than those from the cereals. Large inputs of N fertilizer or N by fixation are required if maize-grain legume cropping system in semiarid Kenya are to be sustained in the long term.
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    URL: http://dx.doi.org/10.1007/BF00307842
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    Growth and nitrogen nutrition of maize (Zea mays L.) in soil treated with the nitrification-inhibiting insecticide Baythroid (1996)
    Springer
    Biology and fertility of soils 23 (1996), S. 161-165 
    Details
    ISSN: 1432-0789
    Keywords: ANI ; Baythroid ; Cyfluthrin ; Insecticide ; 15N ; Nitrification ; N uptake ; Synthetic pyrethroid ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A pot experiment was conducted to compare the uptake and dry matter production potential of NH inf4 sup+ and NO inf3 sup- and to study the effect of Baythroid, a contact poison for several insect pests of agricultural crops, on growth and N uptake of maize (Zea mays L.). Nitrogen was applied as (15NH4)2SO4, K15NO3, or 15NH4NO3 and in one treatment Baythroid was combined with 15NH4NO3. Source of N had, in general, a nonsignificant effect on dry matter and N yield, but uptake of NO inf3 sup- was significantly higher than that of NH inf4 sup+ when both N sources were applied together. Substantial loss of N occurred from both the sources, with NH inf4 sup+ showing greater losses. Baythroid was found to have a significant positive effect on dry matter yield of both root and shoot; N yield also increased significantly. Uptake of N from both the applied and native sources increased significantly in the presence of Baythroid and a substantial added nitrogen interaction (ANI) was determined. The positive effect of Baythroid was attributed to: (1) a prolonged availability of NH inf4 sup+ due to inhibition of nitrification, (2) an increased availability of native soil N through enhanced mineralization, and (3) an enhanced root proliferation.
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    Limitations to using benomyl in evaluating mycorrhizal functioning (1997)
    Springer
    Biology and fertility of soils 25 (1997), S. 163-168 
    Details
    ISSN: 1432-0789
    Keywords: Key words Arbuscular mycorrhiza ; Ectomycorrhiza ; Benomyl ; Colonization ; External hyphae ; Field study ; Glomales ; Zea mays ; Pisolithus tinctorius
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Arbuscular mycorrhizal (AM) grasses compete for nutrients with ectomycorrhizal (EM) pine in the southeastern United States. Our objective was to determine if benomyl could be used to selectively inhibit the function of AM and thereby reduce grass competition in the field. The effects of Benlate (active ingredient: benomyl) in the greenhouse and field were evaluated. No effect was observed on pine inoculated with Pisolithus tinctorius in the greenhouse. Colonized root length of benomyl-treated Zea mays L. plants inoculated with Glomus sp. in the greenhouse remained static over time and the response was not dose dependent at concentrations of 0, 20, 60 and 150kg benomyl ha–1 equivalent. In contrast, colonization of nontreated plants increased over time. In the field, a minimal reduction of grass colonization was observed following four applications of benomyl ranging from 5 to 20kgha–1. We conclude that benomyl can successfully inhibit development of AM fungi under controlled conditions in the greenhouse with no inhibitory effects on the EM fungus P. tinctorius; however, in the field several factors may interfere with the effect of benomyl on AM fungi. These factors include: (a) the presence of ground cover which obstructs penetration of the fungicide to the soil, (b) timing of application in relation to mycorrhizal development, and (c) the application method of benomyl, a soil drench being preferable to a foliar spray.
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    Intron-specific stimulation of anaerobic gene expression and splicing efficiency in maize cells (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 252-258 
    Details
    ISSN: 1617-4623
    Keywords: Key words Anaerobiosis ; Glyceraldehyde-3-phosphate dehydrogenase ; Introns ; Transientgene expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Most of the glyceraldehyde-3-phosphate dehydrogenase (GAPDH) genes characterized in plants and algae to date have one intron very close to the 5′ end of the gene. To study the functional relevance of some of these introns for gene expression we have analysed the influence of three 5′ introns on transient gene expression of the anaerobically inducible maize GapC4 promoter in maize cells. Under aerobic conditions, reporter gene expression is increased in the presence of the first introns of the GapC4 and GapC1 genes, and the first intron of the nuclear encoded chloroplast-specific GapA1 gene. In contrast, the GapC4 intron increases anaerobic gene expression above the level obtained for the intronless construct, while anaerobic expression of constructs harboring the GapA1 and GapC1 introns was similar to the anaerobic expression level of the intronless construct. Splicing analysis revealed that the GapC4 intron is processed more efficiently under anaerobic conditions, while no change in splicing efficiency is observed for the GapC1 and the GapA1 introns when subjected to anaerobic conditions. These results suggest that an increase in splicing efficiency contributes to the anaerobic induction of the maize GapC4 gene.
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    Maize Activator transposase has a bipartite DNA binding domain that recognizes subterminal sequences and the terminal inverted repeats (1997)
    Springer
    Molecular genetics and genomics 254 (1997), S. 219-230 
    Details
    ISSN: 1617-4623
    Keywords: Key words Ac Transposable element ; Zea mays ; DNA binding domain ; Gel retardation assay
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The mobility of maize transposable element Activator (Ac) is dependent on the 11-bp terminal inverted repeats (IRs) and approximately 250 subterminal nucleotides at each end. These sequences flank the coding region for the transposase (TPase) protein, which is required for the transposition reaction. Here we show that Ac TPase has a bipartite DNA binding domain, and recognizes the IRs and subterminal sequences in the Ac ends. TPase binds cooperatively to repetitive ACG and TCG sequences, of which 25 copies are found in the 5′ and 20 copies in the 3′ subterminal regions. TPase affinity is highest when these sites are flanked on the 3′ side by an additional G residue (A/TCGG), which is found at 75% of binding sites. Moreover, TPase binds specifically to the Ac IRs, albeit with much lower affinity. Two mutations within the IRs that immobilize Ac abolish TPase binding completely. The basic DNA binding domain of TPase is split into two subdomains. Binding to the subterminal motifs is accomplished by the C-terminal subdomain alone, whereas recognition of the IRs requires the N-terminal subdomain in addition. Furthermore, TPase is extremely flexible in DNA binding. Two direct or inverted binding sites are bound equally well, and sites that are five to twelve bases apart are similarly well bound. The consequences of these findings for the Ac transposition reaction are discussed.
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    Novel, developmentally specific control of Ds transposition in maize (1997)
    Springer
    Molecular genetics and genomics 256 (1997), S. 158-168 
    Details
    ISSN: 1617-4623
    Keywords: Key words Transposon ; Ac ; Regulation ; Zea mays ; Excision
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plants form their gametes late in somatic development and, as a result, often pass somatic mutations on to their progeny. Classic examples of this process are the germinal revertants of unstable, Ac/Ds transposon-induced kernel mutations in maize: frequent and early reversion events during somatic development are generally correlated with a high frequency of revertant gametes. We have characterized a Ds allele of the maize waxy(wx) gene, wx-m5:CS7, for which the correlation between somatic and germinal reversion frequencies no longer holds. The ability of wx-m5:CS7 (CS7) to produce revertant gametes is suppressed ∼100-fold in comparison with a second Ds allele, wx-m5:CS8 (CS8), which has an identical insertion at Wx and the same frequent and early somatic reversion pattern in endosperm. The excision of Ds from wx is not reduced 100-fold in the somatic tissues of CS7 plants as compared with CS8 plants. Suppressed formation of CS7 revertant gametes is independent of the Ac transposase source and is heritably passed to the embryos of progeny kernels; however, frequent and early somatic reversion is observed again in endosperms of these progeny kernels. This suppression appears to be caused by a dominant mutation in a trans-acting product that can suppress the germinal reversion of other Ds-induced alleles as well; the mutation is tightly linked to Wx but is not in the CS7 Ds itself. Taken together, the data suggest a novel mode of developmental control of Ac/Ds elements by the host plant, suppressing element excision in the shoot meristem.
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    Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 599-608 
    Details
    ISSN: 1617-4623
    Keywords: Nitrate reductase ; Phytochrome ; Phosphorylation ; Protein kinase C ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in darkgrown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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    Creation of ecdysone receptor chimeras in plants for controlled regulation of gene expression (1999)
    Springer
    Molecular genetics and genomics 261 (1999), S. 546-552 
    Details
    ISSN: 1617-4623
    Keywords: Key words Transactivation ; Zea mays ; VP16 ; Nuclear receptors ; Heliothis EcR/GR
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Transformation with a chimeric receptor containing the glucocorticoid transactivation and DNA-binding domains fused to an ecdysteroid receptor ligand-binding domain permits ecdysone agonist-inducible gene expression in monocotyledonous plant cells. The inducible system is based on the specific activation of a chimeric receptor containing the ligand-binding domain of the Heliothis virescens ecdysteroid receptor and the inducer RH5992 (a 20-hydroxyecdysone agonist). RH5992 is an non-steroidal agrochemical with a high specificity for lepidopteran ecdysone receptors. Addition of RH5992 to transformed cells results in high levels of inducible expression in a ligand-specific manner, particularly when the effector receptor is coupled to the strong transactivator VP16. A chimeric construct containing the Drosophila ecdysone ligand-binding domain failed to activate reporter gene activity with RH5992, while activation was observed in the presence of muristeroneA. The system described provides the basis for an inducible gene expression system that is compatible with agricultural use.
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    Completion of the sexual cycle and demonstration of genetic recombination in Ustilago maydis in vitro (1999)
    Springer
    Molecular genetics and genomics 262 (1999), S. 468-472 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsUstilago maydis ; Zea mays ; Corn smut ; Meiosis ; Cell cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The heterobasidiomycetes responsible for plant smuts obligatorily require their hosts for the completion of the sexual cycle. Accordingly, the sexual cycle of these fungi could so far be studied only by infecting host plants. We have now induced Ustilago maydis, the causative agent of corn smut, to traverse the whole life cycle by growing mixtures of mating-compatible strains of the fungus on a porous membrane placed on top of embryogenic cell cultures of its host Zea mays. Under these conditions, mating, karyogamy and meiosis take place, and the fungus induces differentiation of the plant cells. These results suggest that embryogenic maize cells produce diffusible compounds needed for completion of the sexual cycle of U. maydis, as the plant does for the pathogen during infection.
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    Phosphorylation/dephosphorylation steps are key events in the phytochrome-mediated enhancement of nitrate reductase mRNA levels and enzyme activity in maize (1996)
    Springer
    Molecular genetics and genomics 251 (1996), S. 599-608 
    Details
    ISSN: 1617-4623
    Keywords: Key words Nitrate reductase ; Phytochrome ; Phosphorylation ; Protein kinase C ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We provide evidence to show that the increase in nitrate reductase (NR) transcript level stimulated by red light is mediated via a phosphorylation-dependent step. The light-stimulated enhancement of NR transcript level was significantly inhibited by H-7, a protein kinase inhibitor, whereas okadaic acid (OKA), a phosphatase inhibitor, had no effect. Phorbol myristate acetate (PMA), an activator of protein kinase C (PKC) enhanced the NR transcript level in dark-grown leaves. No correlation between changes in NR transcript level and NR activity (NRA) was observed. Inhibition of NRA by OKA and stimulation by H-7 indicated that NRA is increased by dephosphorylating the enzyme. We have identified a protein kinase (C type) that can phosphorylate the purified NR in vitro without the involvement of other accessory proteins. By in vivo labelling with 32P and immunoprecipitation of NR with NR antibodies it was found that in the presence of OKA most NR protein (NRP) was present in phosphorylated state, while with H-7 the reverse was seen. The red (R) and far-red (FR) light reversible experiments suggested that phytochrome (Pfr, an active form) stimulation of NRA is mediated by dephosphorylation of the enzyme, suggesting that Pfr regulates both NR transcription and NRA via phosphorylation/dephosphorylation steps controlled by separate signal transduction pathways.
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    Analysis of Mutator-induced mutations in the Iojap gene of maize (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 216-220 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsiojap ; Chloroplast development ; Transposon ; Robertson's Mutator ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recessive nuclear mutation iojap (ij) in maize produces striped plants with normal chloroplasts in green sectors and poorly developed chloroplasts in the white sectors. The ij mutation is also characterized by an array of additional phenotypic affects which suggests a pivotal role for Ij in chloroplast development. The Ij gene from maize has been isolated; however, the sequence has not provided information on the action of the Ij gene product. As an extension of the analysis of the Ij gene we have generated a number of independent transposon insertion mutations using the Robertson's Mutator (Mu). Insertions were found to be distributed throughout the 5' half of the gene and all showed a similar striping pattern to that of the original ij mutation, ij-ref. While several of the new mutant alleles produced ij-homologous transcripts none produced detectable levels of the Ij polypeptide product. Chloroplast development in some cells appears to be able to proceed in the absence of the Ij polypeptide.
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    Analysis ofMutator-induced mutations in theIojap gene of maize (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 216-220 
    Details
    ISSN: 1617-4623
    Keywords: iojap ; Chloroplast development ; Transposon ; Robertson'sMutator ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recessive nuclear mutationiojap (ij) in maize produces striped plants with normal chloroplasts in green sectors and poorly developed chloroplasts in the white sectors. Theij mutation is also characterized by an array of additional phenotypic affects which suggests a pivotal role forIj in chloroplast development. TheIj gene from maize has been isolated; however, the sequence has not provided information on the action of theIj gene product. As an extension of the analysis of theIj gene we have generated a number of independent transposon insertion mutations using the Robertson'sMutator (Mu). Insertions were found to be distributed throughout the 5′ half of the gene and all showed a similar striping pattern to that of the originalij mutation,ij-ref. While several of the new mutant alleles producedij-homologous transcripts none produced detectable levels of the Ij polypeptide product. Chloroplast development in some cells appears to be able to proceed in the absence of the Ij polypeptide.
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    Evidence for plasma membrane-associated forms of sucrose synthase in maize (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 303-310 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Sucrose synthase ; Plasma membrane ; Cellulose biosynthesis ; Endosperm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Plasma membrane fractions were isolated from maize (Zea mays L.) endosperms and etiolated kernels to investigate the possible membrane location of the sucrose synthase (SS) protein. Endosperms from seedlings at both 12 and 21 days after pollination (DAP), representing early and mid-developmental stages, were used, in addition to etiolated leaf and elongation zones from seedlings. Plasma membrane fractions were isolated from this material using differential centrifugation and aqueous two-phase partitioning. The plasma membrane-enriched fraction obtained was then analyzed for the presence of sucrose synthase using protein blots and activity measurements. Both isozymes SS1 and SS2, encoded by the lociSh1 andSus1, respectively, were detected in the plasma membrane-enriched fraction using polyclonal and monoclonal antisera to SS1 and SS2 isozymes. In addition, measurements of sucrose synthase activity in plasma membrane fractions of endosperm revealed high levels of specific activity. The sucrose synthase enzyme is tightly associated with the membrane, as shown by Triton X-100 treatment of the plasma membrane-enriched fraction. It is noteworthy that the gene products of bothSh1 andSus1 were detectable as both soluble and plasma membrane-associated forms.
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    Temporal relationships betweenZea mays, ostrinia nubilalis (Lep.: Pyralidae) and endophyticBeauveria bassiana (1992)
    Springer
    BioControl 37 (1992), S. 525-536 
    Details
    ISSN: 1573-8248
    Keywords: Beauveria bassiana ; Ostrinia nubilalis ; endophytic relationship ; biological control ; insect pathology ; Zea mays ; Beauveria bassiana ; Ostrinia nubilalis ; lutte biologique ; relation endophyte ; pathologie de l'insecte ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Description / Table of Contents: Résumé Le champignon entomopathogène,Beauveria bassiana (Balsamo) Vuillemin a été épandu sur maïs, au stade cornet (V7) par application foliaire d'une formulation granulée de grits de maïs contenant des conidies ou par injection d'une suspension de conidies. Toutes les plantes ont été infestées à l'aide de larves de la Pyrale du maïs,Ostrinia nubilalis, au stade V7 (cornet), V12 (fin de stade cornet), ou V17 (apparition de la panicule). Les plantes infestées au stade cornet et à la fin du stade cornet ont eu significativement plus de chenilles de Pyrale en train de miner que les plantes infestées au stade début de panicule mâle. Le pourcentage de plantes infestées parB. bassiana n'était pas significativement différent entre ces 3 stades phénologiques. Au fur et à mesure que les plantes se développaient,B. bassiana était isolé de différentes parties de la plante, la moelle étant plus souvent infestée que les ligules. Les applications foliaires deB. bassiana ont entraîné la destruction immédiate de la pyrale chez les plantes infestées au stade cornet. La baisse de l'efficacité deB. bassiana aux stades intermédiaires par comparaison avec son efficacité au moment de la récolte est discutée.
    Notes: Abstract The entomopathogenic fungus,Beauveria bassiana (Balsamo) Vuillemin, was applied to whorl-stage (V7) corn,Zea mays L., by foliar application of a granular formulation of corn grits containing conidia or by injection of a conidial suspension. All plants were infested with European corn borer larvae,Ostrinia nubilalis (Hübner), at the V7 (whorl), V12 (late-whorl), or V17 (pretassel) stage of plant development. Plants infested at whorl and late-whorl stages had significantly more European corn borer tunneling than did plants infested at the pretassel stage. The percentage of plants colonized byB. bassiana did not differ significantly among the whorl, late-whorl, and pretassel stages. As the plants matured,B. bassiana was isolated from different plant areas, with the pith more frequently colonized than the leaf collars. Foliar application ofB. bassiana provided immediate suppression ofO. nubilalis in those plants infested at whorl stage. The reduced efficacy ofB. bassiana at the intermediate plant stages relative to efficacy at harvest is discussed.
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    The ndhH genes of gramminean plastomes are linked with the junctions between small single copy and inverted repeat regions (1990)
    Springer
    Current genetics 18 (1990), S. 245-250 
    Details
    ISSN: 1432-0983
    Keywords: Chloroplast DNA ; Junction between small single copy and inverted repeat regions ; Zea mays ; Grammineae ; ndhH gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The junctions JSA and JSB between the two inverted repeat regions IRA and IRB and the small single copy region of the maize chloroplast DNA have been identified by DNA sequencing. The JSA junction coincides with the initiation codon of the ndhH gene which is encoded by the adjacent region of the small single copy region. A comparison with the plastomes of rice, rye, tobacco and liverwort shows that linkage of this junction with the ndhH gene is specific for gramminean species. The amino acid sequences deduced from the ndhH genes show conserved histidine and cysteine residues which are likely to form a metal-binding domain.
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    Maturation of maize pollen in vitro (1992)
    Springer
    Plant cell reports 11 (1992), S. 535-539 
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    ISSN: 1432-203X
    Keywords: Zea mays ; in vitro culture ; in vitro pollen ; pollen germination ; fertilization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Maturation of maize pollen was obtained in male reproductive structures cultured in vitro. Immature tassels containing microspores at the mid-uninucleate to late-binucleate stage of development were excised and spikelets, anthers, and/or isolated microspores were cultured on a medium capable of supporting pollen maturation. Microspore mitosis, culminating in the production of starch-filled, trinucleate pollen capable of germination, was observed after 7–15 days, depending on the genotype and stage at which the cultures were initiated. Up to 100%, 70%, and 20% of the cultured spikelets, anthers, and isolated microspores, respectively, produced mature pollen, which germinated, however, at different frequencies (i.e., spikelets, 50–70%; anthers, 5–10%; microspores, 〈1%). Mature kernels were produced following fertilization with pollen from cultured spikelets and anthers. These procedures provide methods for the in vitro manipulation of a significant phase of the maize life cycle.
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    Extracellular matrix surface network of embryogenic units of friable maize callus contains arabinogalactan-proteins recognized by monoclonal antibody JIM4 (1999)
    Springer
    Plant cell reports 18 (1999), S. 369-374 
    Details
    ISSN: 1432-203X
    Keywords: Key words Arabinogalactan-proteins ; Somatic embryogenesis ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Embryogenic units of friable maize callus are formed as globular or oblong packets of tightly associated meristematic cells. These units are surrounded by conspicuous cell walls visible in light microscopy after staining with basic fuchsin. Transmission electron microscopy revealed that embryogenic cells are rich in endoplasmic reticulum, polysomes and small protein bodies, and that the outermost layer of their cell walls is composed of fibrillar material. Electron microscopy has also shown that this material covers the surface of embryogenic cells as a distinct layer which we denote as extracellular matrix surface network (ECMSN). Employing histochemical staining with β-glucosyl Yariv phenylglycoside, we localized arabinogalactan-proteins (AGPs) to the outer cell walls of embryogenic units including ECMSN. The most prominent staining was found in cell-cell junction domains. Large non-embryogenic callus cells were not stained with this AGP-specific dye. Immunofluorescence and silver-enhanced immunogold labelling using monoclonal antibody JIM4 has shown that the ECMSN of embryogenic cells is equipped with JIM4 epitope, while non-embryogenic callus cells are devoid of this epitope. We propose that some specific AGPs of the ECMSN might be relevant for cell-cell adhesion and recognition of embryogenic cells during early embryogenic stages, and that the JIM4 antibody can serve as an early marker of embryogenic competence in maize callus culture.
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    Gene transfer to maize male reproductive structure by particle bombardment of tassel primordia (1993)
    Springer
    Plant cell reports 12 (1993), S. 607-611 
    Details
    ISSN: 1432-203X
    Keywords: Transient expression ; Particle bombardment ; Tassel primordia ; In vitro culture ; Anthers ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Maize (Zea mays L.) tassel primordia were used as a target for particle bombardment, to assess the possibility of introducing foreign DNA into male reproductive structures. Transient expression of the β-glucuronidase gene (GUS) or anthocyanin marker genes (C1 and B-Peru) driven by the CaMV 35S promoter was obtained in tassel primordia 24h after bombardment. Gold particles coated with DNA reached stamen primordia tissues, which eventually form the anthers and pollen. Bombarded tassels were also cultured in vitro and GUS activity was detected in the vascular tissue of mature anthers that developed within 4 weeks. This new approach represents a preliminary step toward pollen mediated transformation.
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    Factors affecting in vitro maturation of isolated maize microspores (1993)
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    Plant cell reports 12 (1993), S. 564-568 
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    ISSN: 1432-203X
    Keywords: Zea mays ; In vitro culture ; Isolated microspores ; Pollen development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An in vitro method to simulate pollen development was developed in maize (Zea mays L.). Microspores at the late uninucleate to early binucleate stage were isolated and cultured under various conditions. Cell viability, starch content and the formation of the three nuclei as found in normal mature pollen were monitored during the course of the culture. Media composition was modified in order to promote starch accumulation and frequency of mitosis, while maintaining the viability of the microspores. Under the best conditions, up to 12% of the microspores matured in vitro into trinucleate, starch-filled viable pollen grains which were unable to germinate or produce seeds. At different stages during in vitro maturation, proteins patterns were analyzed and compared with their in vivo equivalent and the patterns were only partially similar.
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    Ploidy variation of pronamide-treated maize calli during long term culture (1993)
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    Plant cell reports 12 (1993), S. 648-651 
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    ISSN: 1432-203X
    Keywords: chromosome doubling ; Zea mays ; tissue culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Anther-derived calli of corn were treated with 10 μM pronamide for 2, 3 and 4 days. The ploidy level of the calli was then evaluated using flow cytometry, at different times after the treatment. Untreated haploid calli did not change in ploidy level for 97 days but by 466 days, there were up to 50% diploid or higher ploidy cells thus showing that spontaneous doubling may occur during corn calli subculture with this genotype. Pronamide treatment did increase the percentage of diploid and tetraploid cells and by 466 days, all of the lines showed an additional change toward higher ploidy levels. This change may be due to spontaneous chromosome doubling or to differential cell cycle times of cells with different ploidy levels. The ploidy level of plants regenerated from the cultures was determined by counting the guard cell chloroplast numbers and the correlation with the ploidy level of the cultures was r2=0.84. These studies show that pronamide treatments can increase haploid maize callus chromosome numbers and that spontaneous chromosome doubling can occur with time in maize callus.
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    Cytosolic calcium regulates a potassium current in corn (Zea mays) protoplasts (1991)
    Springer
    The journal of membrane biology 119 (1991), S. 277-288 
    Details
    ISSN: 1432-1424
    Keywords: Ca2+-activated K+ current ; Ca2+ channel ; Zea mays ; 1,4-dihydropyridine ; phenylalkylamine ; patch clamp
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The voltage- and time-dependent K+ current,I K + out , elicited by depolarization of corn protoplasts, was inhibited by the addition of calcium channel antagonists (nitrendipine, nifedipine, verapamil, methoxyverapamil, bepridil, but not La3+) to the extracellular medium. These results suggested that the influx of external Ca2+ was necessary for K+ current activation. The IC50, concentration of inhibitor that caused 50% reduction of the current, for nitrendipine was 1 μm at a test potential of +60 mV following a 20-min incubation period. In order to test whether intracellular Ca2+ actuated the K+ current, we altered either the Ca2+ buffering capacity or the free Ca2+ concentration of the intracellular medium (pipette filling solution). By these means,I K + out could be varied over a 10-fold range. Increasing the free Ca2+ concentration from 40 to 400nm also shifted the activation of the K+ current toward more negative potentials. Maintaining cytoplasmic Ca2+ at 500nm with 40nm EGTA resulted in a more rapid activation of the K+ current. Thus the normal rate of activation of this current may reflect changes in cytoplasmic Ca2+ on depolarization. Increasing intracellular Ca2+ to 500nm or 1 μm also led to inactivation of the K+ current within a few minutes. It is concluded thatI K + out is regulated by cytosolic Ca2+, which is in turn controlled by Ca2+ influx through dihydropyridine-, and phenylalkylamine-sensitive channels.
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    Matrix-associated DNA from maize is enriched in repetitive sequences (1992)
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    Plant cell reports 11 (1992), S. 355-358 
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    ISSN: 1432-203X
    Keywords: Zea mays ; Matrix-associated ; DNA ; repetitive sequences ; DNA loops
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to elucidate some features of the topological organization of DNA within the plant nucleus, DNA fragments involved in the attachment of the DNA loops to the nuclear matrix in maize were studied. The matrix-associated DNA from dry embryo and meristematic cells after extensive digestion with DNase I and high salt treatment was about 2% of the total DNA, sized within the range of 50 and 250 bp. This DNA was found to be enriched in repetitive DNA sequences, both for nuclei from dry embryo and meristematic cells. The loop size of the DNA in cells of Zea mays appeared to be between 5 and 25 kbp.
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    Electroporation and PEG delivery of DNA into maize microspores (1992)
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    Plant cell reports 11 (1992), S. 567-570 
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    ISSN: 1432-203X
    Keywords: Microspore ; Electroporation ; Transformation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The ability to deliver and detect reporter gene activity in maize microspores was tested. Tested expression vectors contained the chloramphenicol acetyl transferase (CAT) gene and one of the following promoter-intron combinations: 1) cauliflower mosaic virus (CaMV 35S), 2) CaMV 35S + maize alcohol dehydrogenase 1 intron 6 (Adh1-I6), 3) maize alcohol dehydrogenase 1 + intron 1 (Adh1-I1), or 4) maize ubiquitin 1 + intron 1 (Ubiq 1-I1) promoter + intron. The expression vectors were delivered into maize microspores using electroporation or polyethylene glycol (PEG). Both methods were effective for delivering free DNA into microspores. Although all four promoters were active in maize protoplasts, only two promoters were active in maize microspores. The CaMV 35S and the Adh1 promoters did not promote gene expression in maize microspore. The CaMV 35S + Adh1-I6 and Ubiq1-I1 promoters produced high levels of CAT activity in maize microspores.
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    Nitrogen availability alters patterns of accumulation of heat stress-induced proteins in plants (1996)
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    Oecologia 105 (1996), S. 413-418 
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    ISSN: 1432-1939
    Keywords: Zea mays ; Heat-stress ; Heat-shock proteins ; Photosynthesis ; Nutrients
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mounting evidence suggests that heat-shock proteins (HSPs) play a vital role in enhancing survival at high temperature. There is, however, considerable variation in patterns of HSP production among species, and even among and within individuals of a species. It is not known why this variation exists and to what extent variation in HSPs among organisms might be related to differences in thermotolerance. One possibility is that production of HSPs confers costs and natural selection has worked towards optimizing the cost-to-benefits of HSP synthesis and accumulation. However, the costs of this production have not been determined. If HSP production confers significant nitrogen (N) costs, then we reasoned that plants grown under low-N conditions might accumulate less HSP than high-N plants. Furthermore, if HSPs are related to thermotolerance, then variation in HSPs induced by N (or other factors) might correlate with variation in thermotolerance, here measured as short-term effects of heat stress on net CO2 assimilation and photosystem II (PSII) function. To test these predictions, we grew individuals of a single variety of corn (Zea mays L.) under different N levels and then exposed the plants to acute heat stress. We found that: (1) high-N plants produced greater amounts of mitochondrial Hsp60 and chloroplastic Hsp24 per unit protein than their low-N counterparts; and (2) patterns of HSP production were related to PSII efficiency, as measured by F v/F m. Thus, our results indicate that N availability influences HSP production in higher plants suggesting that HSP production might be resource-limited, and that among other benefits, chloroplast HSPs (e.g., Hsp24) may in some way limit damage to PSII function during heat stress.
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    Observations on the subcellular distribution of the ammonium ion in maize root tissue using in-vivo 14N-nuclear magnetic resonance spectroscopy (1991)
    Springer
    Planta 183 (1991), S. 359-367 
    Details
    ISSN: 1432-2048
    Keywords: Ammonium compartmentation ; Cytoplasm ; Vacuole ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We show that the pH dependence of the base-catalysed exchange rate of the ammonium ion provides a basis for discriminating between the cytoplasmic and vacuolar pools of ammonium in plant tissues. In vivo, 14N-nuclear magnetic resonance spectra were recorded with and without 1H-decoupling and information on the subcellular distribution of NH 4 + was obtained from a lineshape analysis of the 1H-coupled spectrum. We applied this method to maize (Zea mays L.) root tissues and found that: (i), the cytoplasmic ammonium concentration was low, which was in accord with the large activity of glutamine synthetase present in the roots; and (ii), inhibition of glutamine synthetase with methionine sulphoximine increased the cytoplasmic ammonium concentration, and led to the appearance of ammonium in the xylem sap.
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    Manipulating cytoplasmic pH under anoxia: A critical test of the role of pH in the switch from aerobic to anaerobic metabolism (1995)
    Springer
    Planta 195 (1995), S. 324-330 
    Details
    ISSN: 1432-2048
    Keywords: Anoxia ; Biochemical pH-stat ; Cytoplasmic pH ; Ethanol production ; Pyruvate decarboxylase ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Ethanol production by maize (Zea mays L.) root tips, measured by an enzymic assay of the suspending medium, was correlated with changes in the cytoplasmic pH, determined by in-vivo 31P nuclear magnetic resonance (NMR) spectroscopy, following the onset of anoxia. Strong evidence for the role of the cytoplasmic pH in triggering the switch to ethanol production under anoxia was obtained by: (i) varying the pH of the suspending medium between pH 4 and pH 10; and (ii) using the permeant weak base methylamine to combat the acidification of the cytoplasm induced by the anoxic conditions. Experimentally, it proved to be much easier to manipulate the cytoplasmic pH under anoxia after the pH had stabilised, rather than during the initial rapid acidification that occurred following the onset of anoxia, and in the presence of methylamine, it was possible to impose a normal aerobic cytoplasmic pH value on tissue that was metabolising anaerobically. By this means it was possible to demonstrate the reversibility of the pH effect on ethanol production under anoxia and thus to provide good evidence in support of the biochemical pH-stat model of the anoxic response. The NMR measurement of the cytoplasmic pH in the presence of methylamine was achieved by using a manganese pretreatment technique to eliminate interference between the cytoplasmic and vacuolar Pi signals, and it seems likely that the experimental approach used here will have further applications in studies of the metabolic response to anoxia.
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    Impact of low-temperature stress on general phenylpropanoid and anthocyanin pathways: Enhancement of transcript abundance and anthocyanin pigmentation in maize seedlings (1994)
    Springer
    Planta 194 (1994), S. 541-549 
    Details
    ISSN: 1432-2048
    Keywords: Anthocyanin ; Cold stress ; mRNA ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Changes in anthocyanin content and transcript abundance for genes whose products function in general phenylpropanoid metabolism and the anthocyanin pathway were monitored in maize (Zea mays L.) seedlings during short-term, low-temperature treatment. Anthocyanin and mRNA abundance in sheaths of maize seedlings increased with the severity and duration of cold. Anthocyanin accumulation was found in all tested lines that were genotypically capable of any anthocyanin production. Within 24 h of transferring 7-d maize (B37N) seedlings to 10° C, phenylalanine ammonia-lyase (Pal) (EC 4.3.1.5)-homologous and chalcone synthase (C2) (EC 2.3.1.74) transcript levels increased at least 8- and 50-fold, respectively, and 4-coumarate:CoA ligase (4Cl) (EC 6.2.1.12)-homologous and chalcone isomerase (Chi) (EC 5.5.1.6)-homologous transcripts increased at least 3-fold over levels in unstressed plants. Time-course studies showed thatPal (EC 4.3.1.5) andC2-transcript levels remained relatively constant for the first 12 h of cold stress, dramatically increased over the next 12 h, and declined to pretreatment levels within 2 d of returning coldstressed seedlings to ambient (25° C) temperature. Transcripts4Cl (EC 6.2.1.12) andChi (EC 5.5.1.6) increased in abundance within 6 h of cold stress, exhibited no further increase over the next 36 h, and declined to pretreatment levels upon returning seedlings to 25° C. Transcripts homologous to two regulatory (R, C1) and three structural (A1,A2, andBz2) anthocyanin genes increased at least 7- to 10-fold during cold treatment, exhibiting similar kinetics of accumulation as forPal (EC 4.3.1.5) andC2 transcripts. Transcripts encoded byBz1, the anthocyanin structural gene for UDP:glucose-flavonol glucosyltransferase (EC 2.4.1.91), were relatively abundant in control tissues and exhibited only a transient increase during the cold period. Our studies suggest that the genes of the anthocyanin biosynthetic pathway can be consideredcor (Cold-Regulation) genes, and because this pathway is well defined, it is an excellent subject for characterizing plant molecular responses to low temperatures.
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    Timing of induced volatile emissions in maize seedlings (1998)
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    Planta 207 (1998), S. 146-152 
    Details
    ISSN: 1432-2048
    Keywords: Key words: Induced defence ; Parasitoid ; Plant-insect interactions ; Semiochemicals ; Volatiles ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Maize (Zea mays L.) releases specific volatiles in response to herbivory by caterpillars. These volatiles are known to serve as cues for parasitic wasps to locate the herbivores. In the present study the exact time of volatile emission after simulated herbivory (mechanical damage and treatment with caterpillar regurgitant) was measured for seedlings of the cultivars “Ioana Sweet Corn” and “LG11”. Odours were collected every 0.5 h for a total of 12 h. Typical “green leaf odours”, (Z)-3-hexenal, (E )-2-hexenal, (Z)-hexen-1-o1, and (Z)-3-hexen-1-yl acetate, were emitted immediately upon damage and their amounts dropped rapidly after the first collections. Several of the induced compounds were released within 2 h after treatment, while others (mainly sesquiterpenoids) started to be released after 4 h. The LG11 seedlings emitted several compounds (e.g. β-myrcene, (Z)-β-ocimene, benzyl acetate, β-caryophyllene, (E,E )-α-farnesene) that were not detected for Ioana. (E,E )-α-farnesene was continuously emitted by LG11 seedlings, even by undamaged plants. Timing of the release of volatile compounds that the two varieties had in common did not differ significantly, with the exception of indole for which the peak production was considerably earlier for LG11. These findings are discussed in the context of biosynthetic pathways and mechanisms involved in induced emissions of plant volatiles and the exploitation of the resulting odour by parasitoids and predators of herbivores.
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    Galactolipase activity but not the level of high-melting-point phosphatidylglycerol is related to chilling tolerance in differentially sensitive Zea mays inbred lines (1998)
    Springer
    Plant cell reports 17 (1998), S. 897-901 
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    ISSN: 1432-203X
    Keywords: Key words Chilling response ; Galactolipase activity ; High-melting-point phosphatidylglycerol ; Lipid degradation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Galactolipase activity, the level of high-melting-point phosphatidylglycerol (HMP-PG) as well as degradation of lipids during chilling and rewarming were studied in seedlings of maize inbred lines with different chilling responses. In aged chloroplasts of chilling-sensitive (CS) lines, galactolipase activity was considerably higher than that determined in aged chloroplasts isolated from chilling-tolerant (CT) ones. Chilling of seedlings at 5 °C for 6 days induced neither loss of chlorophyll content nor visible changes in the leaves, while a slight decline in total acyl lipid content by about 15.5% and 12.5% in CS and CT lines, respectively, was observed. Among total acyl lipids, only monogalactosyldiacylglycerol (MGDG) levels were decreased significantly upon chilling. Following return to the original growth conditions for 4 days, visible chilling injury in seedlings as well as essential differences in the decrease in total acyl lipids by about 53% and 20% in CS and CT lines, respectively, were found. These changes were accompanied by more extensive degradation of MGDG, digalactosyldiacylglycerol and phosphatidylglycerol in CS than in CT lines. As the levels of HMP-PG in fresh leaves were the same in all four lines of maize, it seems that galactolipase activity and not the level of HMP-PG is related to chilling response in maize.
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    URL: http://dx.doi.org/10.1007/s002990050505
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    Denaturing gradient gel electrophoresis identifies genomic DNA polymorphism with high frequency in maize (1990)
    Springer
    Theoretical and applied genetics 80 (1990), S. 1-10 
    Details
    ISSN: 1432-2242
    Keywords: Denaturing gradient gel electrophoresis ; DNA polymorphism ; Restriction fragment length polymorphism ; Zea mays ; B-A translocation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have used denaturing gradient gel electrophoresis (DGGE) to identify genomic DNA polymorphism in maize (Zea mays L.). DGGE probes detect polymorphism in maize at a frequency comparable to the incidence of restriction fragment length polymorphism (RFLP). Probes identifying polymorphism were mapped to maize chromosome arms by utilizing DGGE and maize lines carrying B-A chromosomal translocations. The methods for library construction, probe screening, and genome analysis, described here for maize, can also be applied to the genomic analysis of other organisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00224008
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    Chromosomal and cell size analysis of cold tolerant maize (1992)
    Springer
    Theoretical and applied genetics 84 (1992), S. 798-802 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; C-banding ; Cell size ; Chloroplast number ; Cold tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary C-band number, guard cell length, and chloroplast number per guard cell were determined for eight maize populations. These populations consisted of maize selected for cold tolerance at the University of Nebraska as well as the original unselected populations. The genome size of these populations had previously been determined. C-band number fluctuated concertedly with the changes in genome size indicating that deletions and additions of constitutive heterochromatin occurred during selection, resulting in altered genome sizes. Guard cell size of all the cold tolerant populations was greater than the cell size of the respective nonselected populations. Chloroplast number per guard cell was also higher in all the cold tolerant populations than in their parental populations, but the increases were not statistically significant. The results indicate that changes in genome size that occurred during selection for cold tolerance are the result of changes in amounts of C-band heterochromatin and that the selection process results in an increase in cell size in the cold tolerant populations.
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    URL: http://dx.doi.org/10.1007/BF00227387
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    Haplo-diploid gene expression and pollen selection for tolerance to acetochlor in maize (1994)
    Springer
    Theoretical and applied genetics 88 (1994), S. 780-784 
    Details
    ISSN: 1432-2242
    Keywords: Acetochlor tolerance ; Gene expression Pollen selection ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The objectives of this research were to determine if genes controlling the reaction to the herbicide acetochlor in maize (Zea mays L.) are active during both the haploid and the diploid phases of the life cycle and if pollen selection can be utilized for improving sporophytic resistance. Pollen of eight inbred lines, previously characterized through sporophytic analysis for the level of tolerance to acetochlor, showed a differential reaction to the herbicide forin vitro tube length; moreover, such pollen reactions proved to be significantly correlated (r =0.786*,df=6) with those of the sporophytes producing the pollen. Pollen analysis of two inbred lines (i.e. Mo17, tolerant, and B79, susceptible) and their single cross showed that thein vitro pollen-tube length reaction of the hybrid was intermediate between those of two parents. An experiment on pollen selection was then performed by growing tassels of Mo17xB79 in the presence of the herbicide. Pollen obtained from treated tassels showed a greater tolerance to acetochlor, assessed asin vitro tube length reaction, than pollen obtained from control tassels. Moreover, the backcross [B79 (Mo17xB79)] sporophytic population obtained using pollen from the treated tassels was more tolerant (as indicated by the fresh weight of plants grown in the presence of the herbicide) than was the control backcross population. The two populations did not differ when grown without the herbicide. These findings indicate that genes controlling the reaction to acetochlor in maize have haplodiploid expression; consequently, pollen selection can be applied for improving plant tolerance.
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    URL: http://dx.doi.org/10.1007/BF01253986
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    Cytological and molecular characterization of oat×maize partial hybrids (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 123-135 
    Details
    ISSN: 1432-2242
    Keywords: Key wordsAvena sativa ; Zea mays ; Wide hybridization ; Genomic in situ hybridization ; Cytogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In cereals, interspecific and intergeneric hybridizations (wide crosses) which yield karyotypically stable hybrid plants have been used as starting points to widen the genetic base of a crop and to construct stocks for genetic analysis. Also, uniparental genome elimination in karyotypically unstable hybrids has been utilized for cereal haploid production. We have crossed hexaploid oat (2n=6x=42, Avena sativa L.) and maize (2n=2x=20, Zea mays L.) and recovered 90 progenies through embryo rescue. Fifty-two plants (58%) produced from oat×maize hybridization were oat haploids (2n=3x=21) following maize chromosome elimination. Twenty-eight plants (31%) were found to be stable partial hybrids with 1–4 maize chromosomes in addition to a haploid set of 21 oat chromosomes (2n=21+1 to 2n=21+4). Ten of the ninety plants produced were found to be apparent chromosomal chimeras, where some tissues in a given plant contained maize chromosomes while other tissues did not, or else different tissues contained a different number of maize chromosomes. DNA restriction fragment length polymorphisms (RFLPs) were used to identify the maize chromosome(s) present in the various oat-maize progenies. Maize chromosomes 2, 3, 4, 5, 6, 7, 8, and 9 were detected in partial hybrids and chromosomal chimeras. Maize chromosomes 1 and 10 were not detected in the plants analyzed to-date. Furthermore, partial self-fertility, which is common in oat haploids, was also observed in some oat-maize hybrids. Upon selfing, partial hybrids with one or two maize chromosomes showed nearly complete transmission of the maize chromosome to give self-fertile maize-chromosome-addition oat plants. Fertile lines were recovered that contained an added maize chromosome or chromosome pair representing six of the ten maize chromosomes. Four independently derived disomic maize chromosome addition lines contained chromosome 4, one line carried chromosome 7, two lines had chromosome 9, one had chromosome 2, and one had chromosome 3. One maize chromosome-8 monosomic addition line was also identified. We also identified a double disomic addition line containing both maize chromosomes 4 and 7. This constitutes the first report of the production of karyotypically stable partial hybrids involving highly unrelated species from two subfamilies of the Gramineae (Pooideae – oat, and Panicoideae – maize) and the subsequent recovery of fertile oat-maize chromosome addition lines. These represent novel material for gene/ marker mapping, maize chromosome manipulation, the study of maize gene expression in oat, and the transfer of maize DNA, genes, or active transposons to oat.
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    URL: http://dx.doi.org/10.1007/s001220050257
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    Cytological and molecular characterization of oat x maize partial hybrids (1996)
    Springer
    Theoretical and applied genetics 93 (1996), S. 123-135 
    Details
    ISSN: 1432-2242
    Keywords: Avena sativa ; Zea mays ; Wide hybridization ; Genomic in situ hybridization ; Cytogenetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In cereals, interspecific and intergeneric hybridizations (wide crosses) which yield karyotypically stable hybrid plants have been used as starting points to widen the genetic base of a crop and to construct stocks for genetic analysis. Also, uniparental genome elimination in karyotypically unstable hybrids has been utilized for cereal haploid production. We have crossed hexaploid oat (2n=6x=42, Avena sativa L.) and maize (2n=2x=20, Zea mays L.) and recovered 90 progenies through embryo rescue. Fifty-two plants (58%) produced from oatxmaize hybridization were oat haploids (2n=3x=21) following maize chromosome elimination. Twenty-eight plants (31%) were found to be stable partial hybrids with 1–4 maize chromosomes in addition to a haploid set of 21 oat chromosomes (2n=21+1 to 2n=21+4). Ten of the ninety plants produced were found to be apparent chromosomal chimeras, where some tissues in a given plant contained maize chromosomes while other tissues did not, or else different tissues contained a different number of maize chromosomes. DNA restriction fragment length polymorphisms (RFLPs) were used to identify the maize chromosome(s) present in the various oat-maize progenies. Maize chromosomes 2, 3, 4, 5, 6, 7, 8, and 9 were detected in partial hybrids and chromosomal chimeras. Maize chromosomes 1 and 10 were not detected in the plants analyzed to-date. Furthermore, partial self-fertility, which is common in oat haploids, was also observed in some oat-maize hybrids. Upon selfing, partial hybrids with one or two maize chromosomes showed nearly complete transmission of the maize chromosome to give self-fertile maize-chromosome-addition oat plants. Fertile lines were recovered that contained an added maize chromosome or chromosome pair representing six of the ten maize chromosomes. Four independently derived disomic maize chromosome addition lines contained chromosome 4, one line carried chromosome 7, two lines had chromosome 9, one had chromosome 2, and one had chromosome 3. One maize chromosome-8 monosomic addition line was also identified. We also identified a double disomic addition line containing both maize chromosomes 4 and 7. This constitutes the first report of the production of karyotypically stable partial hybrids involving highly unrelated species from two subfamilies of the Gramineae (Pooideae — oat, and Panicoideae — maize) and the subsequent recovery of fertile oat-maize chromosome addition lines. These represent novel material for gene/ marker mapping, maize chromosome manipulation, the study of maize gene expression in oat, and the transfer of maize DNA, genes, or active transposons to oat.
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    URL: http://dx.doi.org/10.1007/BF00225737
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    Dynamic gene action at QTLs for resistance to Setosphaeria turcica in maize (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 1036-1045 
    Details
    ISSN: 1432-2242
    Keywords: Key words Exserohilum turcicum ; Maize ; Northern corn leaf blight ; Quantitative resistance ; QTL mapping ; Setosphaeria turcica ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Cultivars with quantitative resistance are widely used to control Setosphaeria turcica (Luttrell) Leonard & Suggs, the causal organism of northern corn leaf blight (NCLB). Here the effectiveness of quantitative trait loci (QTLs) for NCLB resistance was investigated over the course of host plant development in inoculated field trials. A population of 194–256 F2:3 lines derived from a cross between a susceptible Italian (Lo951) and a highly resistant African inbred line (CML202) was tested in three environments in Kenya. The traits assessed were the incubation period (IP), the percentage disease severity (DS 1 to 5, taken biweekly), and the area under the disease progress curve (AUDPC). Considering all resistance traits and environments, a total of 19 putative QTLs were detected by composite interval mapping using a linkage map with 110 RFLP markers. In the combined analysis across environments, nine QTLs were significant (LOD 〉3.0) for DS 3, recorded around flowering time, explaining 71% of the genotypic variance. Four of these nine QTLs displayed significant (P〈0.05) QTL×environment (QTL×E) interaction. Most QTLs were already significant in the juvenile stage (IP) and became less effective after flowering. Across environments, three QTLs conditioned adult-plant resistance, in the sense that they were only significant after flowering. Six QTL alleles on chromosomes 2, 4, 5, 8, and 9 of CML202 should be useful for marker-assisted backcrossing.
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    URL: http://dx.doi.org/10.1007/s001220051165
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    Genetic analysis of tolerance to low-phosphorus stress in maize using restriction fragment length polymorphisms (1991)
    Springer
    Theoretical and applied genetics 82 (1991), S. 561-568 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Restriction fragment length polymorphisms (RFLPs)-Phosphorus (P) stress-quantitative trait loci (QTLs)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary An understanding of the genetic nature underlying tolerance to low-phosphorus (low-P) stress could aid in the efficient development of tolerant plant strains. The objective of this study was to identify the number of loci in a maize (Zea mays L.) population segregating for tolerance to low-P stress, their approximate location, and the magnitude of their effect. Seventy-seven restriction fragment length polymorphisms (RFLPs) were identified and scored in a maize F2 population derived from a cross between line NY821 and line H99. The F2 individuals were self-pollinated to produce F3 families. Ninety F3 families were grown in a sand-alumina system, which simulated diffusion-limited, low-P soil conditions. The F3 families were evaluated for vegetative growth in a controlled-environment experiment. To identify quantitative trait loci (QTLs) underlying tolerance to low-P stress, the mean phenotypic performances of the F3 families were contrasted based on genotypic classification at each of 77 RFLP marker loci. Six RFLP marker loci were significantly associated with performance under low-P stress (P〈0.01). One marker locus accounted for 25% of the total phenotypic variation. Additive gene action was predominant for all of the QTLs identified. Significant marker loci were located on four separate chromosomes representing five unlinked genomic regions. Two marker loci were associated with an additive by additive epistatic interaction. A multiple regression model including three marker loci and the significant epistatic interaction accounted for 46% of the total phenotypic variation. Heterozygosity per se was not predictive of phenotypic performance.
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    URL: http://dx.doi.org/10.1007/BF00226791
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    The CAT-2 null phenotype in maize is likely due to a DNA insertion into the Cat2 gene (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 635-640 
    Details
    ISSN: 1432-2242
    Keywords: Catalase null ; Zea mays ; Catalase transcript ; Transposable element
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The molecular basis for a shorter Cat2 transcript in maize lines null for the CAT-2 catalase iso/yme was investigated using cDNA libraries and genomic DNA blots. Sequence comparison of partial Cat2 cDNAs obtained from two CAT-2 null lines and a wild-type CAT-2 encoding cDNA showed that the Cat2 null transcripts diverged from the wild-type transcript but remained homologous to each other. Genomic DNA blots indicated that the missing portion of the transcript is present in the genomes of lines null for the CAT-2 isozyme. Differences in the hybridization patterns of normal and null lines were revealed when genomic DNA blots were probed with the full-length Cat2 cDNA, a Cat2 gene-specific probe, and a “null sequence” probe. Together, the DNA blotting results suggest that a rearrangement of the Cat2 gene has occurred in the CAT-2 null lines. The available data suggest that the CAT-2 null mutation in maize is due to a DNA insertion into the Cat2 gene.
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    URL: http://dx.doi.org/10.1007/BF00226730
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    Genetic basis of resistance to sugarcane mosaic virus in European maize germplasm (1998)
    Springer
    Theoretical and applied genetics 96 (1998), S. 1151-1161 
    Details
    ISSN: 1432-2242
    Keywords: Key words European maize ; Zea mays ; Sugarcane mosaic virus ; Disease resistance ; RFLP
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Sugarcane mosaic virus (SCMV) causes considerable damage to maize (Zea mays L.) in Europe. The objective of the present study was to determine the genetic basis of resistance to SCMV in European maize germplasm and to compare it with that of U.S. inbred Pa405. Three resistant European inbreds D21, D32, and FAP1360A were crossed with four susceptible inbreds F7, KW1292, D408, and D145 to produce four F2 populations and three backcrosses to the susceptible parent. Screening for SCMV resistance in parental inbreds and segregating generations was done in two field trials as well as under greenhouse conditions. RFLP markers umc85, bnl6.29, umc10, umc44, and SSR marker phi075 were used in F2 populations or F3 lines to locate the resistance gene(s) in the maize genome. Segregation in the F2 and backcross generations fitted to different gene models depending on the environmental conditions and the genotype of the susceptible parent. In the field tests, resistance in the three resistant European inbreds seems to be controlled by two to three genes. Under greenhouse conditions, susceptibility to SCMV in D32 appears to be governed by one dominant and one recessive gene. Allelism tests indicated the presence of a common dominant gene (denoted as Scm1) in all three resistant European inbreds and Pa405. Marker analyses mapped two dominant genes: Scm1 on chromosome 6S and Scm2 on chromosome 3.
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    URL: http://dx.doi.org/10.1007/s001220050851
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    QTLs for resistance to Setosphaeria turcica in an early maturing Dent×Flint maize population (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 649-655 
    Details
    ISSN: 1432-2242
    Keywords: Key words Corn ; Exserohilum turcicum ; Northern corn leaf blight ; Quantitative resistance ; QTL mapping ; Setosphaeria turcica ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Quantitative trait loci (QTLs) for resistance to the fungal pathogen Setosphaeria turcica, the cause of northern corn leaf blight (NCLB), were mapped in a population of 220 F3 families derived from a cross between two moderately resistant European inbred lines, D32 (dent) and D145 (flint). The population was genotyped with 87 RFLP and 7 SSR markers. Trials were conducted in the field in Switzerland, and in the greenhouse with selected F3 families in Germany. The F3 population segregated widely for resistance with transgression of the parents. By composite interval mapping, a total of 13 QTLs were detected with two disease ratings (0 and 3 weeks after flowering). Together these QTLs explained 48% and 62% of the phenotypic variation. Gene action at most QTLs was partially dominant. Eight out of the 13 QTL alleles for resistance were contributed by the more-resistant parent, D145. On chromosomes 3, 5 and 8, QTLs were located in the same chromosomal regions as QTLs in tropical and U.S. Corn Belt germplasm. Some QTLs affected NCLB, head smut and common rust at the same time, with alleles at these loci acting isodirectionally.
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    URL: http://dx.doi.org/10.1007/s001220051280
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    The use of antimicrotubule herbicides for the production of doubled haploid plants from anther-derived maize callus (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 205-211 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Chromosome doubling ; Amiprophos methyl ; Pronamide ; Oryzalin ; Trifluralin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four antimicrotubule herbicides, amiprophosmethyl (APM), pronamide, oryzalin, and trifluralin, were evaluated for their ability to induce chromosome doubling in anther-derived, haploid maize callus. Effects of various herbicide treatments on the growth and regenerative capacity of callus along with the ploidy and seed set of regenerated plants were determined. Flow cytometric analysis was also used to measure changes in ploidy levels of callus cells following treatments. More than 50% of the cells were doubled in chromosome number after the haploid callus was treated with 5 or 10 μ M APM or 10 μ M pronamide for 3 days. A similar proportion of plants regenerated from the treated callus produced seed upon self-pollination. APM and pronamide did not inhibit callus growth at these concentrations and the treated callus retained a high plant regeneration capacity. Oryzalin very effectively induced chromosome doubling, but severely inhibited the growth of regenerable callus and plant regeneration. Trifluralin induced chromosome doubling in a small proportion of cells at lower concentrations (0.5 and 1 μ M), however, at a higher concentration (5 μM) it inhibited callus growth and plant regeneration. The results indicate that APM and pronamide may be useful agents for inducing chromosome doubling of anther-derived maize haploid callus at very low concentrations.
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    URL: http://dx.doi.org/10.1007/BF00215724
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    Parentage determination in maize hybrids using the arbitrarily primed polymerase chain reaction (AP-PCR) (1991)
    Springer
    Theoretical and applied genetics 82 (1991), S. 473-476 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Parentage determination ; Varietal identification ; Genetic polymorphisms ; Genetic markers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using a novel procedure based on the polymerase chain reaction, we have developed a rapid, efficient, and economical method for identifying plant genotypes. The arbitrarily primed polymerase chain reaction (AP-PCR) generates reproducible fingerprints from any organism, without the need for DNA sequence information. These fingerprints include DNA fragment polymorphisms that can be (1) used for varietal identification and parentage determination, (2) followed in segregating populations produced by crosses, (3) used as markers for the construction of genetic maps, and (4) used to generate dendograms of phylogenetic relationships, especially at the intraspecific level. AP-PCR requires only minute quantities of DNA (10–25 ng per reaction) and therefore can be used in situations in which DNA is limiting. We demonstrate the use of AP-PCR to identify inbred parents of hybrid maize plants in double-blind experiments.
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    URL: http://dx.doi.org/10.1007/BF00588601
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    Expression of the catalase and superoxide dismutase genes in mature pollen in maize (1990)
    Springer
    Theoretical and applied genetics 80 (1990), S. 705-711 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Catalase ; Gene expression ; Pollen ; superoxide dismutase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The expression of the Cat and Sod genes encoding the multiple catalases and superoxide dismutases in maize has been studied in maize pollen at anther dehiscence. Pollen from three catalase activity variant inbred lines was examined. Zymorgram analysis, immunoassays, and RNA blots show that, in the lines used, only the CAT-1 catalase isozyme is expressed in mature pollen; the CAT-2 and CAT-3 isozymes are not. The data presented further demonstrate that the Cat1 gene is transcribed and translated after tetrad formation. The relative protein levels of the various superoxide dismutase (SOD) isozymes appear to be similar in pollen and scutella, and correspond to the relatively low levels observed for the different Sod transcripts in these tissues. The presence of “double” transcripts for Sod3 and Sod4A is discussed.
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    URL: http://dx.doi.org/10.1007/BF00224233
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    Molecular markers for plant breeding: comparisons of RFLP and RAPD genotyping costs (1993)
    Springer
    Theoretical and applied genetics 86 (1993), S. 975-984 
    Details
    ISSN: 1432-2242
    Keywords: Chemiluminescence ; Genotyping costs ; RAPD ; RFLP ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three molecular marker protocols, chemiluminescent restriction fragment length polymorphisms (c-RFLPs), radioactivity-based restriction fragment length polymorphisms (r-RFLPs), and randomly amplified DNA polymorphisms (RAPDs) were compared in terms of cost and time efficiency. Estimates of cost of supplies and time requirements were obtained from simulations of maize (Zea mays L.) genotyping experiments utilizing protocols currently in use. The increase in total cost with increasing numbers of individuals genotyped and markers analyzed is higher for RAPDs than for RFLPs. RAPDs were generally found to be more cost and time efficient for studies involving small sample sizes, while RFLPs have the advantage for larger sample sizes. Because of the shorter exposure times involved, c-RFLPs require less time than r-RFLPs to obtain a given amount of information. Variations in the protocols, such as number of re-uses of Southern blots or cost of Taq DNA polymerase per reaction of amplification, also affect the relative merits of RAPDs and RFLPs. Two examples were analyzed where molecular markers are used: a germ plasm survey and quantitative trait loci (QTL) mapping in a segregating population. No protocol was found to be the most cost and time efficient over the entire range of sample sizes and number of marker loci studied.
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    URL: http://dx.doi.org/10.1007/BF00211050
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    Phylogenetic analysis of Sorghum and related taxa using internal transcribed spacers of nuclear ribosomal DNA (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 26-32 
    Details
    ISSN: 1432-2242
    Keywords: Sorghum ; Zea mays ; Phylogeny rDNA sequence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The phylogenetic relationships of the genus Sorghum and related genera were studied by sequencing the nuclear ribosomal DNA (rDNA) internal transcribed spacer region (ITS). DNA was extracted from 15 Sorghum accessions, including one accession from each of the sections Chaetosorghum and Heterosorghum, four accessions from Parasorghum, two accessions from Stiposorghum, and seven representatives from three species of the section Sorghum (one accession from each of S. propinquum and S. halepense, and five races of S. bicolor). The maize (Zea mays) line, H95, and an accession from Cleistachne sorghoides were also included in the study. Variable nucleotides were used to construct a strict consensus phylogenetic tree. The analyses indicate that S. propinquum, S. halepense and S. bicolor subsp. arundinaceum race aethiopicum may be the closest wild relatives of cultivated sorghum; Sorghum nitidum may be the closest 2n=10 relative to S. bicolor, the sections Chaetosorghum and Heterosorghum appear closely related to each other and more closely related to the section Sorghum than Parasorghum; and the section Parasorghum is not monophyletic. The results also indicate that the genus Sorghum is a very ancient and diverse group.
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    URL: http://dx.doi.org/10.1007/BF00226978
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    Estimation of sampling variance of molecular marker data using the bootstrap procedure (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 259-264 
    Details
    ISSN: 1432-2242
    Keywords: RFLP ; Bootstrap ; Sampling variance ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Knowledge of genetic relationships among genotypes is useful in a plant breeding program because it permits the organization of germplasm and provides for more efficient sampling. The genetic distance (GD) among genotypes can be estimated using random restriction fragment length polymorphisms (RFLPs) as molecular markers. Knowledge of the sampling variance associated with RFLP markers is needed to determine how many markers are required for a given level of precision in the estimate of GD. The sampling variance for GD among all pairs of 37 maize (Z. mays L.) inbred lines was estimated from 1202 RFLPs. The 1202 polymorphisms were generated from 251 enzyme-probe combinations (EPC). The sampling variance was used to determine how large a sample of RFLPs was required to provide a given level of precision. The coefficient of variation (CV) associated with GD has a nearly linear relationship between its expected standard deviation and mean. The magnitude of the decrease in the mean CV for GD with increasing numbers of bands was dependent upon the sampling unit; e.g., individual polymorphic bands vs EPC, and the degree of relatedness among the inbreds compared. The rate of reduction in mean CV with increasing sample size was the same regardless of the restriction enzyme used, BamHI, EcoRI or HindIII, when the bootstrap sampling units were individual polymorphic bands. In constrast, although the rate of reduction (slopes) was the same, the intercepts of the mean CVs were different when EPCs were used as the bootstrap sampling unit. This difference was due to the higher number of bands per EPC in BamHI (4.94) compared with EcoRI (4.83) and HindIII (4.63).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00225151
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    Detection of the apomictic mode of reproduction in maize-Tripsacum hybrids using maize RFLP markers (1995)
    Springer
    Theoretical and applied genetics 90 (1995), S. 1198-1203 
    Details
    ISSN: 1432-2242
    Keywords: Diplospory ; RFLP ; Bulk-segregant analysis ; Genome similarity ; Intergeneric hybrids ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Polyploid plants in the genus Tripsacum, a wild relative of maize, reproduce through gametophytic apomixis of the diplosporous type, an asexual mode of reproduction through seed. Moving gene(s) responsible for the apomictic trait into crop plants would open new areas in plant breeding and agriculture. Efforts to transfer apomixis from Tripsacum into maize at CIMMYT resulted in numerou intergeneric F1 hybrids obtained from various Tripsacum species. A bulk-segregant analysis was carried out to identify molecular markers linked to diplospory in T. dactyloides. This was possible because of numerous genome similarities among related species in the Andropogoneae. On the basis of maize RFLP probes, three restriction fragments co-segregating with diplospory were identified in one maize-Tripsacum dactyloides F1 population that segregated 1∶1 for the mode of reproduction. The markers were also found to be linked in the maize RFLP map, on the distal end of the long arm of chromosome 6. These results support a simple inheritance of diplospory in Tripsacum. Manipulation of the mode of reproduction in maize-Tripsacum backcross generations, and implications for the transfer of apomixis into maize, are discussed.
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    URL: http://dx.doi.org/10.1007/BF00222943
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  • 85
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    RFLP mapping of the maize gametophytic restorer-of-fertility locus (rf3) and aberrant pollen transmission of the nonrestoring rf3 allele (1997)
    Springer
    Theoretical and applied genetics 95 (1997), S. 525-531 
    Details
    ISSN: 1432-2242
    Keywords: Key words Cytoplasmic male sterility ; Mitochondria ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Cytoplasmic male sterility (CMS) is the maternally inherited inability to produce functional pollen. The Rf3 allele of the nuclear gene rf3 gametophytically restores male fertility to maize plants with the S-type of CMS. The rf3 locus is on the long arm of maize chromosome two (2L). Using 2L RFLPs and three-point mapping analysis we showed that the rf3 locus is located an estimated 4.3 cM distal to the whp locus and 6.4 cM proximal to the bnl17.14 locus. This information was used in combination with RFLPs on two additional maize chromosomes to show that Rf3/rf3 CMS-S plants may aberrantly transmit the nonrestoring allele, rf3, through the male gametophyte.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050593
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    Genetic diversity and its relationship to hybrid performance in maize as revealed by RFLP and AFLP markers (1998)
    Springer
    Theoretical and applied genetics 96 (1998), S. 219-227 
    Details
    ISSN: 1432-2242
    Keywords: Key words DNA polymorphisms ; Genetic distances ; Molecular markers ; Yield prediction ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The challenge to maize breeders is to identify inbred lines that produce highly heterotic hybrids. In the present study we surveyed genetic divergence among 13 inbred lines of maize using DNA markers and assessed the relationship between genetic distance and hybrid performance in a diallel set of crosses between them. The parental lines were assayed for DNA polymorphism using 135 restriction fragment length polymorphisms (RFLPs) and 209 amplified-fragment polymorphisms (AFLPs). Considerable variation among inbreds was detected with RFLP and AFLP markers. Moreover AFLPs detect polymorphisms more efficiently in comparison to RFLPs, due to the larger number of loci assayed in a single PCR reaction. Genetic distances (GDs), calculated from RFLP and AFLP data, were greater among lines belonging to different heterotic groups compared to those calculated from lines of the same heterotic group. Cluster analysis based on GDs revealed associations among lines which agree with expectations based on pedigree information. The GD values of the 78 F1 crosses were partioned into general (GGD) and specific (SGD) components. Correlations of GD with F1 performance for grain yield were positive but too small to be of predictive value. The correlations of SGDs, particularly those based on AFLP data, with specific combining-ability effects for yield may have a practical utility in predicting hybrid performance.
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    URL: http://dx.doi.org/10.1007/s001220050730
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  • 87
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    Mapping of QTL for downy mildew resistance in maize (1999)
    Springer
    Theoretical and applied genetics 99 (1999), S. 519-523 
    Details
    ISSN: 1432-2242
    Keywords: Key words Downy mildew ; Marker-assisted selection ; Quantitative trait loci ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Quantitative trait loci (QTLs) of maize involved in mediating resistance to Peronosclerospora sorghi, the causative agent of sorghum downy mildew (SDM), were detected in a population of recombinant inbred lines (RILs) derived from the Zea mays L. cross between resistant (G62) and susceptible (G58) inbred lines. Field tests of 94 RILs were conducted over two growing seasons using artificial inoculation. Heritability of the disease reaction was high (around 70%). The mapping population of the RILs was also scored for restriction fragment length polymorphic (RFLP) markers. One hundred and six polymorphic RFLP markers were assigned to ten chromosomes covering 1648 cM. Three QTLs were detected that significantly affected resistance to SDM combined across seasons. Two of these mapped quite close together on chromosome 1, while the third one was on chromosome 9. The percentage of phenotypic variance explained by each QTL ranged from 12.4% to 23.8%. Collectively, the three QTLs identified in this study explained 53.6% of the phenotypic variation in susceptibility to the infection. The three resistant QTLs appeared to have additive effects. Increased susceptibility was contributed by the alleles of the susceptible parent. The detection of more than one QTL supports the hypothesis that several qualitative and quantitative genes control resistance to P. sorghi.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051265
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  • 88
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    Application of a stability statistic to international maize yield trials (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 162-165 
    Details
    ISSN: 1432-2242
    Keywords: Genotype x environment interaction ; Stability ; Maize ; Zea mays ; Heterogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Genotype x environment (GE) interaction encountered in experiments complicates genotype selection and varietal recommendation. The integration of yield and stability of genotypes into a single parameter may make selection and recommendation easier. Kang developed a rank-sum method that allows selection for both yield and the stability variance statistics (σ i 2 or s i 2 ) of Shukla. The objective of this research was to compare the rank-sum selection method to selection based on yield alone in five international maize (Zea mays L.) yield trials. Ranks were assigned for yield (the highest mean yield received a rank of 1) and for σ i 2 and s i 2 (the lowest value received a rank of 1). The yield and σ i 2 ranks and/or the yield and s i 2 ranks for each genotype were summed. Each trial contained two reference entries (REs). Yield rank or rank-sum of each genotype was compared to yield rank or rank-sum of the best RE (BRE). GE interaction was significant for all trials. Heterogeneity in the GE interaction due to the linear effect of a covariate (differences in fertility and/or cultural practices) was significant in Trials 1, 2, and 5. Overall, in all trials, 29 genotypes were selected on the basis of yield alone. On the basis of σ i 2 and yield rank-sum, 32 genotypes were identified, with 11 being lower yielding than the 29 yield-based selections. On the basis of s i 2 and yield rank-sum, 31 genotypes were selected, with 11 being lower yielding than the yield-bases selections. Obviously, yield is sacrificed when the rank-sum method is used in the selection process. However, selection based on yield alone may not be adequate when GE interaction is significant because of testing in diverse environments.
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    URL: http://dx.doi.org/10.1007/BF00215718
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  • 89
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    A recombination hotspot in the maize A1 intragenic region (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 185-188 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Recombination ; A1 locus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We find that recombination between two alleles of the maize A1 locus that contain transposon insertions at known molecular positions can occur at 0.04–0.08 cM per kbp (centimorgan per kilobase pair), which is two orders of magnitude higher than the recombination rate for the whole maize genome. It is however, close to the rates found within the bronze locus, another maize structural gene for which both genetic and molecular data are available. This observation supports the idea that the genome consists of regions that are highly recombinogenic — in some cases, at least, structural genes — interspersed with regions that are less recombinogenic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00215721
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  • 90
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    RFLP analysis of Zea mays callus cultures and their regenerated plants (1991)
    Springer
    Theoretical and applied genetics 81 (1991), S. 227-232 
    Details
    ISSN: 1432-2242
    Keywords: Callus cultures ; RFLP ; Zea mays ; Oryza sativa ; Regeneration ; Somaclonal variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Tissue culture of the Zea mays inbred line A188 resulted in the regeneration of plants having a high level of phenotypic variation compared to seed-grown control plants. To determine how such variation was induced and whether this could be related to specific in vitro culture methods, callus cultures were established and maintained on different, commonly used culture media. Plants were regenerated and the genomic DNA of callus cultures and regenerants analysed for RFLP differences. The results show that regardless of the gene probe used, callus formation resulted in significant deviations from the DNA pattern normally found in seed-grown control plants. Alterations in gene copy number also occurred. As differentiation and organogenesis began, the level of DNA variation fell, and most of the regenerated plants showed a genetic similarity to the controls; those with RFLP differences were the somaclonal variants.
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    URL: http://dx.doi.org/10.1007/BF00215727
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  • 91
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    Genetic and amino-acid analysis of two maize threonine-overproducing, lysine-insensitive aspartate kinase mutants (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 767-774 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Aspartate kinase Threonine-overproducing mutants ; Lysine ; Methionine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The aspartate-derived amino-acid pathway leads to the production of the essential amino-acids lysine, methionine, threonine and isoleucine. Aspartate kinase (AK) is the first enzyme in this pathway and exists in isoforms that are feedback inhibited by lysine and threonine. Two maize (Zea mays L.) threonine-overproducing, lysine-insensitive AK mutants (Ask1-LT19 and Ask2-LT20) were previously isolated. The present study was conducted to determine the map location of Ask2 and to examine the amino-acid profiles of the Ask mutants. The threonine-overproducing trait conferred by Ask2-LT20 was mapped to the long arm of chromosome 2. Both mutants exhibited increased free threonine concentrations (nmol/mg dry weight) over wild-type. The percent free threonine increased from approximately 2% in wild-type kernels to 37–54% of the total free amino-acid pool in homozygous mutant kernels. Free methionine concentrations also increased significantly in homozygous mutants. Free lysine concentrations were increased but to a much lesser extent than threonine or methionine. In contrast to previous studies, free aspartate concentrations were observed to decrease, indicating a possible limiting factor in threonine synthesis. Total (free plus protein-bound) amino-acid analyses demonstrated a consistent, significant increase in threonine, methionine and lysine concentrations in the homozygous mutants. Significant increases in protein-bound (total minus free) threonine, methionine and lysine were observed in the Ask mutants, indicating adequate protein sinks to incorporate the increased free amino-acid concentrations. Total amino-acid contents (nmol/kernel) were approximately the same for mutant and wild-type kernels. In five inbred lines both Ask mutations conferred the threonine-overproducing phenotype, indicating high expressivity in different genetic backgrounds. These analyses are discussed in the context of the regulation of the aspartate-derived amino-acid pathway.
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    URL: http://dx.doi.org/10.1007/BF00223717
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    Identification of opaque-2 genotypes in segregating populations of Quality Protein Maize by analysis of restriction fragment length polymorphisms (1994)
    Springer
    Theoretical and applied genetics 89 (1994), S. 407-412 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Opaque-2 ; RFLPs Marker-assisted selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Quality Protein Maize (QPM) is a name given to genetically modified opaque-2 maize with hard endosperm. The opaque-2 mutation conditions a reduction in the amount of zein seed storage protein; zeins are deficient in the essential amino acids lysine and tryptophan, and mutant seed have a higher nutritional value. To utilize the potential of opaque-2 maize, elite inbreds can be converted to o2/o2 forms and subsequently to hard endosperm opaque-2. Since opaque-2 is recessive and endosperm specific, conventional backcross procedures to convert elite inbreds to opaque-2 forms are inefficient. To alleviate this problem, a marker-assisted selection procedure was developed for the Texas A&M University Quality Protein Maize breeding program. Hybridization of an O2 cDNA probe to blots of DNA from plants carrying O2 and o2 alleles showed that restriction fragment length polymorphisms (RFLPs) exist between the W64A o2 allele and O2 alleles of Mo17 and TX5855 inbred lines. To identify the opaque2 genotypes in segregating populations, an RFLP marker assay combining the O2 cDNA probe and HindIII-digestion of genomic DNA was developed. The effectiveness of the O2 RFLP marker assay was tested under field conditions using F2 and backcross populations of several hard endosperm opaque-2 lines. A comparison of the genotypes identified by RFLP analysis with the seed phenotypes of the next generation indicated that this procedure is accurate and can be used for identifying O2/O2, O2/o2, and o2/o2 genotypes of individual juvenile plants in breeding populations.
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    URL: http://dx.doi.org/10.1007/BF00225374
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    Comparative mapping in F2∶3 and F6∶7 generations of quantitative trait loci for grain yield and yield components in maize (1996)
    Springer
    Theoretical and applied genetics 92 (1996), S. 817-826 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; RFLPs ; Plant breeding ; Genetics ; Recombination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This study was conducted to compare maize quantitative trait loci (QTL) detection for grain yield and yield components in F2∶3 and F6∶7 recombinant inbred (RI) lines from the same population. One hundred and eighty-six F6∶7 RIs from a Mo17×H99 population were grown in a replicated field experiment and analyzed at 101 loci detected by restriction fragment length polymorphisms (RFLPs). Single-factor analysis of variance was conducted for each locus-trait combination to identify QTL. For grain yield, 6 QTL were detected accounting for 22% of the phenotypic variation. A total of 63 QTL were identified for the seven grain yield components with alleles from both parents contributing to increased trait values. Several genetic regions were associated with more than one trait, indicating possible linked and/or pleiotropic effects. In a comparison with 150 F2∶3 lines from the same population, the same genetic regions and parental effects were detected across generations despite being evaluated under diverse environmental conditions. Some of the QTL detected in the F2∶3 seem to be dissected into multiple, linked QTL in the F6∶7 generation, indicating better genetic resolution for QTL detection with RIs. Also, genetic effects at QTL are smaller in the F6∶7 generation for all traits.
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    URL: http://dx.doi.org/10.1007/BF00221893
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    Micromanipulation and in vitro fertilization with single pollen grains of maize (1990)
    Springer
    Sexual plant reproduction 3 (1990), S. 160-169 
    Details
    ISSN: 1432-2145
    Keywords: Pollen ; In vitro germination ; Microinjection ; In vitro fertilization ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The manipulation of single pollen grains of maize was studied. The effects of delivering substances both locally to the grain wall, tube or tip by a microcapillary and directly into the pollen grain by microinjection, and single grain pollination were investigated. Germination was induced by adding small amounts of water locally to the grains with either a microcapillary or with a waterdelivering emulsion without any other ingredients in the medium. The grains were overlayered by mineral or silicone oil so that tube growth proceeded without the grains bursting. There was no apparent penetration of high-molecular-weight substances (FITC-dextran, ethidium bromide labelled DNA) into the living grain either before or after pollination. Neither could the penetration of these substances be detected in both dry, viable and hydrated grains, tubes and tube tips, with or without treatment with Triton X-100 and dimethyl sulfoxide. By microinjection, however, the delivery of high-molecular-weight substances into grains was possible. Such injected grains successfully pollinated stigmas of cultured ear segments. Pollination with pore-injected grains was most efficient (mean 26%). No difference in fertilization rates between mass pollination (mean 41%) and single grain pollination (mean 39%) could be found. A mean fertilization rate of 29% could be obtained after microinjection. Seedlings developed 3 weeks after being pollinated by means of the in vitro pollination and fertilization method.
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    URL: http://dx.doi.org/10.1007/BF00205225
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    Regulation of flower development in cultured ears of maize (Zea mays L.) (1990)
    Springer
    Sexual plant reproduction 3 (1990), S. 109-115 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Ear initials ; Kinetin ; Gibberellic acid ; Male and female flowers ; Development
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Young ears of maize were cultured in two different liquid media containing either kinetin (KN) or kinetin + gibberellic acid (KN + GA3) in order to manipulate stamen and gynoecium development. In KN medium, stamens developed and gynoecia aborted in the flowers of the cultured immature ears. In the KN + GA3 medium, however, ovaries with silks developed and stamens aborted. These differential morphological events were recorded with SEM photomicrographs at regular intervals after excision of ear inflorescences. In addition, the mitotic activity in the developing or aborting organs was determined over a 75-h period. It increased from 6% to 14% in developing organs (i.e. stamens in KN medium, and gynoecia in KN + GA3 medium) and gradually decreased to 1% in the degenerating organs (i.e. gynoecia in KN medium, and stamens in KN + GA3 medium) by 45 h of culture. The mitotic activity reached zero in degenerating flower organs by 75 h of culture. Whether these differential sensitivities to the exogenously applied members of these two plant growth regulator classes are unique to our in vitro system or reflect a more general control feature of in vivo inflorescences must await further clarification.
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    URL: http://dx.doi.org/10.1007/BF00198854
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    Analysis of pollen-tube growth in cultured maize silks (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 227-231 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Maize ; Pollen-tube growth regulation ; In vitro pollination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary In vitro pollen-tube growth in maize was studied using an in vitro pollination system. In the ‘cut-silk’ method, ovaries with silks were placed on medium in vitro, whereafter the silk was cut and the upper part of the silk was pollinated. Pollen tubes were not able to bridge the space between the two silk parts. Even when silk parts were tightly connected, pollen tubes still were not able to pass the cut ends and reach the lower silk part. Pollen-tube growth rates and the direction of tube growth were not influenced by the presence or absence of an ovary. Prepollination did not have any influence on pollen-tube growth rate. Measurements of pollen-tube growth rate also showed that there was no ‘population effect’, i.e. growth rate was not stimulated by pollination with an excess of pollen grains. We found that the direction in which maize pollen grew was determined only by the positioning of the silk hairs.
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    URL: http://dx.doi.org/10.1007/BF00189816
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    RNA and protein synthesis in sperm cells isolated from Zea mays L. pollen (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 239-243 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Sperm cell ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sperm cells are thought to be quiescent in pollen and activated upon pollen germination. To test this hypothesis, protein, RNA and DNA synthesis were assessed in Zea mays sperm cells at different times after isolation from pollen. Protein synthesis changed with time; while some proteins were found to be constitutive in both 0 and 24 h cells, others were synthesized and some disappeared. Overall, the number of proteins detected at 24 h doubled compared with freshly isolated cells. Incorporation of [3H]leucine in 24 h cells was about 50 times that in freshly isolated cells, and that of [5, 6-3H]uridine, about 7 times. Very low incorporation of [6-3H]thymidine into the cells was detected; there was no difference between freshly isolated and 24 h cells. It is possible that the differences in synthetic activity between freshly isolated and 24-h-old cells might correspond to sperm cell activation during pollen tube growth. If so, these metabolic changes may play an important role in fertilization.
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    URL: http://dx.doi.org/10.1007/BF00231900
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    Cleavage polyembryony in maize (1992)
    Springer
    Sexual plant reproduction 5 (1992), S. 224-226 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Maize ; Polyembryony
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two types of cleavage polyembryony are described in the inbred line VIR 17 of maize. Suspensorial embryony was observed to occur spontaneously. Typical cleavage of the zygotic proembryo occurred spontaneously, but could also be induced by treating the developing caryopses with 2,4-Dichlorophenoxyacetic acid (2,4-D) on the second day after pollination. 2,4-D was active as a decorelative factor also evoking the expression of totipotency in individual proembryonal cells.
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    URL: http://dx.doi.org/10.1007/BF00189815
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    Effects of calcium, magnesium, potassium and boron on sperm cells isolated from pollen of Zea mays L. (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 113-122 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Calcium ; Cell integrity ; Cell viability ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our previous studies showed that Brewbaker and Kwack salts, which have been widely used in pollen germination and sperm isolation, are not appropriate for the maintenance of isolated maize (Zea mays L.) sperm cells. In the present study, we have characterized the effects of each BKS component salt on the integrity of isolated sperm cells using hemacytometry. At 0.01 and 0.1 mM, there were no differences in cell number between control and any salt-treated cells except a 22% decrease with 0.1 mM MgSO4 at 48 h. At the 1 mM level, cell number decreased with time in the presence of Ca(NO3)2 and MgSO4, with loss of integrity of most cells at 48 h, while KNO3 and H3BO3 had little or no effect. Further characterization of calcium-induced reduction in cell integrity using flow cytometry showed that depletion of possible residual free calcium by addition of EGTA to the suspension medium improved cell longevity and viability. Exposure of isolated sperm cells to 1 mM calcium had no effect on cell integrity and viability in 5 h; however, only 12% of cells remained intact at 24 h. The reduction in cell integrity was hastened when cells were pretreated with the calcium ionophore A23187 prior to exposure to 1 mM calcium, with a 54% reduction in cell number at 1 h and complete cell lysis at 24 h. However, depletion of cytosolic free calcium by pretreatment of cells with the calcium ionophore followed by resuspension in the presence of EGTA resulted in rapid reduction of cell integrity as well. These results collectively suggest that maize sperm cells are sensitive to exogenous free calcium; however, a certain level of cytosolic free calcium is necessary for maintenance of integrity. Mechanisms of calcium-induced reduction in cell integrity are discussed along with possible roles of the sensitivity of sperm cells to calcium in fertilization.
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    URL: http://dx.doi.org/10.1007/BF00230898
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  • 100
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    New lights in early steps of in vitro fertilization in plants (1996)
    Springer
    Sexual plant reproduction 9 (1996), S. 324-329 
    Details
    ISSN: 1432-2145
    Keywords: Key words In vitro fertilization ; Gamete recognition ; Gamete fusion ; Egg activation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Studies using in vitro fertilization systems in animals and lower plants have led to a better understanding of the initial steps of fertilization and their underlying mechanisms. These mechanisms remain to be elucidated in flowering plants. Recent progress related to the development of in vitro fertilization systems using maize as a plant model is presented in this review. Their potential for leading to a better understanding of the process of gametic recognition and fusion and of the early events triggering egg activation and zygote formation are also discussed.
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    URL: http://dx.doi.org/10.1007/s004970050050
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