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  • Zea mays  (78)
  • Springer  (78)
  • American Meteorological Society
  • Oxford University Press
  • Periodicals Archive Online (PAO)
  • 1995-1999
  • 1990-1994  (78)
  • 1935-1939
  • 1994  (45)
  • 1991  (33)
Collection
Keywords
Publisher
  • Springer  (78)
  • American Meteorological Society
  • Oxford University Press
  • Periodicals Archive Online (PAO)
  • Wiley-Blackwell  (1)
Years
  • 1995-1999
  • 1990-1994  (78)
  • 1935-1939
Year
  • 1
    Electronic Resource
    Electronic Resource
    Examination of anAspergillus flavus resistant inbred of maize for crossresistance to sap beetle vectors (1994)
    Springer
    Entomologia experimentalis et applicata 71 (1994), S. 177-180 
    Details
    ISSN: 1570-7458
    Keywords: aflatoxin ; Carophilus ; Zea mays ; corn ; plant resistance ; Coleoptera ; Nitidulidae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02382385
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  • 2
    Electronic Resource
    Electronic Resource
    Biological activity of maize leaf extracts against the African armyworm,Spodoptera exempta (1994)
    Springer
    Entomologia experimentalis et applicata 72 (1994), S. 17-23 
    Details
    ISSN: 1570-7458
    Keywords: plant varietal resistance ; armyworm ; Spodoptera exempta ; leaf extracts ; Zea mays ; feeding deterrent ; toxicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Maize (Zea mays L.) leaf tissue of cv Bastille and cv Michoacan 12 was extracted with n-hexane. The extracts were bioassayed against 5th instar African armyworm,Spodoptera exempta (Walker)(Lepidoptera: Noctuidae), by feeding the larvae on agar based media or sucrose impregnated glass fibre discs. The hexane extract of the ‘resistant’ cv Bastille exhibited feeding deterrency and toxicity which were not shown by the ‘susceptible’ cv Michoacan 12. The hexane extract of cv Bastille was adsorbed onto silica gel, the solution filtered off and the adsorbed component taken up into ethyl acetate. Bioassay of these fractions indicated that the toxic and deterrent action was retained in the ethyl acetate fraction. Preparative thin layer chromatography of the ethyl acetate fraction isolated two biologically active constituents. These were both growth inhibitors and lethal by ingestion to the 5th instar African armyworm. Implications for resistance in maize varieties to insect pests are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02382411
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  • 3
    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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  • 4
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647671
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  • 5
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00197734
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  • 6
    Electronic Resource
    Electronic Resource
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00714468
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  • 7
    Electronic Resource
    Electronic Resource
    In vitro fertilization of single, isolated gametes of maize mediated by electrofusion (1991)
    Springer
    Sexual plant reproduction 4 (1991), S. 12-16 
    Details
    ISSN: 1432-2145
    Keywords: In vitro fertilization ; Egg cell ; Sperm cell ; Electrofusion ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electrofusion-mediated in vitro fertilization of maize using single sperm and egg cells was performed. Sperm cells were released from pollen grains after rupture of the latter by osmotic shock in the fusion medium (0.55 M mannitol). Egg cells were isolated by enzyme treatment (pectinase, pectolyase, hemicellulase, and cellulase) followed by mechanical isolation. The conditions generally used for the electrical fusion of protoplasts of somatic cells were also applied to the protoplasts of gametic cells of maize. Electrofusion was performed with single pairs of gametes under microscopic observation. The mean fusion frequency was 79%. Isolated egg cells of maize showed protoplasmic streaming during 22 days of culture, but they did not divide. However, after fusion of the sperm with the egg cells, these fused cells did develop, with a mean division frequency of 83%, and grew to multicellular structures. Egg cells and fusion products were cultivated with a maize feeder-cell system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00194565
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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
    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.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00418663
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  • 10
    Electronic Resource
    Electronic Resource
    Molecular cloning of two different cDNAs for maize acetyl CoA carboxylase (1994)
    Springer
    Plant molecular biology 24 (1994), S. 35-49 
    Details
    ISSN: 1573-5028
    Keywords: acetyl CoA carboxylase ; cDNA Cloning ; herbicide ; nucleotide sequence ; purification ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Acetyl CoA carboxylase (EC 6.4.1.2) in plants is a chloroplast-localized, biotin-containing enzyme that catalyses the carboxylation of acetyl CoA to malonyl CoA, the first committed step of the fatty acid biosynthesis pathway. Acetyl CoA carboxylase is the target site for the monocotyledon-specific aryloxy-phenoxypropionate and cyclohexanedione groups of herbicides. We have purifed a herbicide-sensitive acetyl CoA carboxylase from maize leaves to homogeneity (specific activity 7 μmol min-1 mg-1), separating it during the purification from a minor herbicide-resistant acetyl CoA carboxylase. The purified enzyme is a dimer of 230 kDa subunits. Antibodies raised to the purified acetyl CoA carboxylase detected three cross-reacting clones in a maize leaf cDNA expression library, each having an insert of 4–4.5 kb. Restriction analysis and sequencing showed that the cDNAs were derived from two different transcripts. Comparison of the deduced amino acid sequences with those of chicken and yeast acetyl CoA carboxylases confirmed that both types encoded acetyl CoA carboxylase, corresponding to the C-terminal half of the enzyme. The overall identity of the maize and chicken sequences was 37% (58% similarity) but for some shorter regions was much higher. Analysis of six other acetyl CoA carboxylase clones recovered from the maize cDNA library showed four belonged to one type and two to the other. The nucleotide sequence similarity between the two types of cDNA was approximately 95% in the coding region but considerably less in the 3′-untranslated region. Northern blot analysis of maize RNA showed a single band of 8.2–8.5 kb for acetyl CoA carboxylase mRNA. Southern blot hybridisations indicated that there are probably no more than two genes in maize for acetyl CoA carboxylase. The possible significance of two different cDNAs for acetyl CoA carboxylase is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040572
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  • 11
    Electronic Resource
    Electronic Resource
    Molecular analysis of wild-type and mutant alleles at the Opaque-2 regulatory locus of maize reveals different mutations and types of O2 products (1994)
    Springer
    Plant molecular biology 24 (1994), S. 949-959 
    Details
    ISSN: 1573-5028
    Keywords: Opaque-2 and opaque-2 genes ; allelic diversity ; Opaque-2 proteins ; transcriptional activator ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The expression of the various members of the zein multigene family in maize endosperm is controlled by different regulatory loci. One of these loci, Opaque-2, coding for a bZIP transcriptional factor, controls the expression of a subset of zein genes. Analysis of genomic DNA from plants carrying wild-type (O2) or mutant o2 alleles shows specific DNA restriction patterns that correlate with transcript types and their various gene products. Northern and western analyses show the presence in different wild types of a 1.7 kb transcript coding for different sizes of normal O2 proteins that migrate as doublets in the 68–72 kDa range. Among the various o2 mutants analysed we showed the occurrence of various null-transcript alleles, the presence of alleles with a normal size transcript which, however, produce a different-sized o2 protein, and a mutant producing both a normal size transcript and a longer transcript, but generating only a single o2 product migrating around 40 kDa. Analysis of other mutations (o7, fl2) known to affect zien polypeptide synthesis shows no interference of these mutations in the expression of the O2 gene products. The overall results indicate the occurrence of micro heterogeneity in the O2 wild-type genes and a broad spectrum of o2 mutations, both producing different sizes of O2 or o2 proteins. A nomenclature of the O2 and o2 genes based on the RFLP, transcripts and products of the various alleles is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00014448
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  • 12
    Electronic Resource
    Electronic Resource
    Analysis of the cytosolic hsp70 gene family inZea mays (1994)
    Springer
    Plant molecular biology 25 (1994), S. 909-916 
    Details
    ISSN: 1573-5028
    Keywords: heat shock 70 kDa protein ; multigene family ; polymerase chain reaction ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In this study we have analysed the multigene family coding for the cytoplasmic heat shock 70 kDa proteins (hsp70) inZea mays. Fully degenerate primers were used in a polymerase chain reaction (PCR) to amplify selected regions of the hsp70 genes. Sequence and Southern blot analysis reveals that at least three highly conserved genes exist in maize. In addition, amplification reveals the presence of a conserved intron in all genes examined. Expression analysis shows that the hsp70 genes studied represent members of the inducible and constitutive families. The results obtained may indicate that there are subfamilies of cytoplasmic hsp70 genes expressed in higher plants.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028885
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  • 13
    Electronic Resource
    Electronic Resource
    A maize gene expressed during embryogenesis is abscisic acid-inducible and highly conserved (1991)
    Springer
    Plant molecular biology 16 (1991), S. 919-923 
    Details
    ISSN: 1573-5028
    Keywords: Zea mays ; maize ; embryogenesis ; abscisic acid ; seed maturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated by differential hybridization a cDNA, termed Emb564, which is complementary to an 800 nt embryo-specific transcript in Zea mays. The expression of Emb564 can be enhanced by exogenous abscisic acid (ABA) and the effect of ABA on the accumulation of Emb564 transcript appears to be confined to embryos at the early and mid embryonic stages. In addition, Emb564 is expressed at low levels in ABA-deficient but not in ABA non-responsive embryos. Genomic analysis suggested that the Emb564 mRNA is encoded by a single gene. Sequence analysis showed that Emb564 exhibits extensive similarities with several known ABA-inducible genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00015086
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  • 14
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    Isolation of a cytochrome P450 homologue preferentially expressed in developing inflorescences ofZea mays (1994)
    Springer
    Plant molecular biology 25 (1994), S. 343-353 
    Details
    ISSN: 1573-5028
    Keywords: cytochrome P450 ; flower development ; meristem-specific gene ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Four cDNA clones exhibiting preferential hybridization to transcripts present in developing maize tassels were isolated by differential screening. One of these cDNA clones hybridizes to transcripts detectable only in the shoot apex. The abundance of this transcript is significantly higher in developing inflorescence apices than in vegetative apices. DNA sequence analysis of a 2107 nucleotide cDNA clone corresponding to this transcript revealed that the transcript encodes a polypeptide of 547 amino acids, with a molecular mass of 58.4 kDa. This polypeptide shares significant sequence similarity with members of the cytochrome P450 monooxygenase gene superfamily, including the conserved C-terminal domains typical of the cytochrome P450 monooxygenases.
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    URL: http://dx.doi.org/10.1007/BF00043864
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  • 15
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    Stability of the maize chromosomal high-mobility-group proteins, HMGa and HMGb,in vivo (1994)
    Springer
    Plant molecular biology 25 (1994), S. 565-568 
    Details
    ISSN: 1573-5028
    Keywords: chromatin ; high-mobility-group (HMG) proteins ; protein stability ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromosomal non-histone high-mobility-group (HMG) proteins represent essential components of eukaryotic chromatin and have also been isolated from a variety of plants. In maize, studies on structure and function of the two larger of the four major HMG proteins have recently been performed and are now extended by analysis of theirin vivo stability using pulse-chase experiments in a cell suspension culture. The half-life of the analyzed HMGa and HMGb proteins was found to be 65 h or more than 78 h, respectively.
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    URL: http://dx.doi.org/10.1007/BF00043885
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  • 16
    Electronic Resource
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    Large tandem duplication associated with aMu2 insertion inZea mays B-Peru gene (1994)
    Springer
    Plant molecular biology 25 (1994), S. 817-828 
    Details
    ISSN: 1573-5028
    Keywords: B-Peru ; germinal revertants ; Mutator ; tandem duplication ; unequal recombination ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Theb locus ofZea mays encodes a transcriptional activator of the anthocyanin biosynthetic pathway. TheB-Peru allele is expressed in the aleurone layer of the seed, which results in dark purple pigmentation of this tissue. An unstableMutator-inducedB-Peru mutant allele,b-Perum220, displays weak, variable pigment and a high germinal reversion rate not characteristic of otherMutator insertions. Characterization of relevant regions ofb-Perum220 revealed aMu2 element insertion in one copy of a 534 bp sequence. This 534 bp sequence is tandemly triplicated in the progenitorB-Peru allele, upstream of theB-Peru transcription start site. In addition to theMu2 insertion, theb-Perum220 allele contains a newly formed large tandem duplication of 4.0 kb, which includes the promoter region and the first three exons of theB-Peru gene. TheMu2 element does not reside at any of the duplication breakpoints. The molecular study of eleven independent germinal revertants revealed five structural classes including structures in which the 4.0 kb tandem duplication is partially or completely deleted, theMu2 element is partially or completely deleted, or a combination of these events has occurred. We hypothesize that most of the revertants arose by unequal recombination between the duplicated regions. Based on these structural analyses, models are discussed to explain the reducedb gene expression inb-Perum220.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028876
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  • 17
    Electronic Resource
    Electronic Resource
    Identification of a maize root transcript expressed in the primary response to nitrate: characterization of a cDNA with homology to ferredoxin-NADP+ oxidoreductase (1994)
    Springer
    Plant molecular biology 26 (1994), S. 679-690 
    Details
    ISSN: 1573-5028
    Keywords: primary response ; ferredoxin NADP+ oxidoreductase ; nitrate ; cycloheximide ; Zea mays ; roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract To more fully understand the biochemical and molecular events which occur in plants exposed to nitrate, cDNAs whose accumulation was enhanced in nitrate- and cycloheximide-treated maize (Zea mays L. W64A × W182E) roots were isolated. The 340 bp Zmrprn 1 (for Zea mays root primary response to nitrate) cDNA also hybridized with a probe enriched for nitrate-induced sequences, and was characterized further. Sequence analysis of a near full-length cDNA (Zmrprn 1A) showed strong homology (〉90% amino acid identity) with a root ferredoxin-NADP+ oxidoreductase (FNR) of rice, and 45–50% amino acid identity with leaf FNR genes. When expressed in Escherichia coli, the Zmrprn 1A cDNA produced a protein with NADPH: ferricyanide reductase activity, consistent with the enzymatic properties of an FNR. The Zmrprn 1 cDNA hybridized with a 1.4 kb transcript which was expressed in the maize root primary response to nitrate. That is, mRNA levels in roots increased rapidly and transiently in response to external nitrate, and low levels of nitrate (10 μM) induced transcript accumulation. The accumulation of the Zmrprn 1 transcript was not prevented by cycloheximide, indicating that the cellular factor(s) required for expression were constitutively present in maize roots. The Zmrprn 1 mRNA accumulated specifically in response to nitrate, since neither K+ nor NH4 + treatment of roots caused transcript accumulation. Maize leaves had about 5% of the transcript level found in roots, indicating a strong preference for expression of Zmrprn 1 in roots. Analysis of maize genomic DNA indicated the presence of only a single gene or very small gene family for the Zmrprn 1. Together, the data indicate that Zmrprn 1A encodes a nitrate regulated maize root FNR.
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    URL: http://dx.doi.org/10.1007/BF00013753
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  • 18
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    Root- and shoot-specific responses of individual glutamine synthetase genes of maize to nitrate and ammonium (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1935-1946 
    Details
    ISSN: 1573-5028
    Keywords: glutamine synthetase genes ; regulation ; nitrate ; ammonium ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The responses of the five cytosolic-type glutamine synthetase (GS1) genes of maize to treatment of hydroponically grown seedlings with 10 mM KNO3 or 10 mM NH4Cl were analyzed. Non-coding 3′ gene-specific hybridization probes and radioanalytic imaging were used to quantitate individual gene transcript levels in excised roots and shoots before treatment and at selected times after treatment. Genes GS1−1 and GS1−2 exhibited distinct organ-specific responses to treatment with either nitrogen source. The GS1−1 transcript level increased over three-fold in roots, but changed little if any in shoots. In contrast, the GS1−2 transcript level increased over two-fold in shoots, but decreased in roots after treatment. Increased transcript levels were evident at 4 h after treatment with either nitrogen source, with maximum accumulations present at 8 h after treatment with ammonium and at 10–12 h after treatment with nitrate. The GS1−3 gene transcript level showed little or no change after treatment with either nitrogen source. The GS1−4 gene transcript level remained constant in shoots of treated seedlings, whereas in roots, it exhibited relatively minor, but complex responses to these two nitrogen sources. The GS1−5 gene transcript is present in very small amounts in seedlings, making it difficult to analyze its response to metabolites in young plants. These results provide support for the possibility that different cytosolic GS genes of maize play distinct roles in nitrogen metabolism during plant growth and differentiation.
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    URL: http://dx.doi.org/10.1007/BF00019504
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    Nucleotide sequence and characterization of a maize cytoplasmic ribosomal protein S11 cDNA (1991)
    Springer
    Plant molecular biology 17 (1991), S. 265-268 
    Details
    ISSN: 1573-5028
    Keywords: cDNA sequence ; cytoplasmic ribosomes ; gene copy number ; ribosomal protein S11 ; steadystate mRNA level ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We isolated a Zea mays cDNA encoding the 40S subunit cytoplasmic ribosomal protein S11. The nucleotide sequence was determined and the derived amino acid sequence compared to the corresponding Arabidopsis thaliana protein showing an homology of 90%. This ribosomal protein is encoded by a small multigene family of at least two members. The mRNA steady-state level is about one order of magnitude higher in rapidly growing parts of the plant such as the roots and shoots of seedlings compared to fully expanded leaf tissue.
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    URL: http://dx.doi.org/10.1007/BF00039502
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    Capturing of host DNA by a plant retroelement: Bs1 encodes plasma membrane H+-ATPase domains (1994)
    Springer
    Plant molecular biology 25 (1994), S. 137-140 
    Details
    ISSN: 1573-5028
    Keywords: DNA acquisition ; retrotransposon ; retrovirus ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The recently identified maize retroelement Bs1 encodes domains of the plasma membrane H+-ATPase. This is the first example of host DNA captured by a plant retroelement and resembles the acquisition of oncogenes by vertebrate retroviruses. The ability to capture sequences from its host provides plant retroelements with a mechanism to alter gene structure which could be important for evolutionary adaptive change.
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    URL: http://dx.doi.org/10.1007/BF00023232
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  • 21
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    In vivo analysis of intron processing using splicing-dependent reporter gene assays (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1785-1795 
    Details
    ISSN: 1573-5028
    Keywords: intron ; maize ; splicing ; vectors ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanisms of intron recognition and processing have been well-studied in mammals and yeast, but in plants the biochemistry of splicing is not known and the rules for intron recognition are not clearly defined. To increase understanding of intron processing in plants, we have constructed new pairs of vectors, pSuccess and pFail, to assess the efficiency of splicing in maize cultured cells. In the pFail series we use translation of pre-mRNA to monitor the amount of unspliced RNA. We inserted an ATG codon in the Bz2 (Bronze-2) intron in frame with luciferase: this construct will express luciferase activity only when splicing fails. In the pSuccess series the spliced message is monitored by inserting an ATG upstream of the Bz2 intron in frame with luciferase: this construct will express luciferase activity only when splicing succeeds. We show here, using both the wild-type Bz2 intron and the same intron with splice site mutations, that the efficiency of splicing can be estimated by the ratio between the luciferase activities of the vector pairs. We also show that mutations in the unique U-rich motif inside the intron can modulate splicing. In addition, a GC-rich insertion in the first exon increases the efficiency of splicing, suggesting that exons also play an important role in intron recognition and/or processing.
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    URL: http://dx.doi.org/10.1007/BF00019492
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    Cloning and characterization of maize herbicide safener-induced cDNAs encoding subunits of glutathione S-transferase isoforms I, II and IV (1994)
    Springer
    Plant molecular biology 26 (1994), S. 1855-1866 
    Details
    ISSN: 1573-5028
    Keywords: Glutathione S-transferase ; herbicide safener ; inducible gene expression ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Several GSTs have been characterised in maize. GST I is a homodimer of 29 kDa subunits, GST II a hetrodimer of 27 kDa and 29 kDa subunits and GST IV a homodimer of 27 kDa subunits. We report the isolation and characterization of a herbicide-safener inducible cDNA clone, GST-27. Based on partial amino acid sequence, GST-27 encodes the 27 kDa subunit present in both glutathione S-transferase isoforms GST II and IV. Northern blotting was used to compare the expression patterns of GST-27 with that of GST-29. Transcripts corresponding to GST-27 were found to be constitutively expressed in RNA isolated from the root, but no expression was detected in RNA isolated from aerial parts of the plant. The application of herbicide safener caused a dramatic increase in the expression of GST-27 in all aerial plant parts tested. GST-29 was found to be constitutively expressed in RNA isolated from a number of maize tissues. The basal level of GST-29 expression showed a minimal increase upon herbicide safener treatment. Although a range of hormonal, environmental and physiological stimuli failed to elevate GST-27 levels, some increase in GST-27 mRNA was observed in the late stages of leaf senescence and after treatments resulting in phytotoxic effects.
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    URL: http://dx.doi.org/10.1007/BF00019498
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  • 23
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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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    URL: http://dx.doi.org/10.1007/BF01868732
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    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.
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    URL: http://dx.doi.org/10.1007/BF00202343
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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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    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).
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    URL: http://dx.doi.org/10.1007/BF00225151
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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.
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    URL: http://dx.doi.org/10.1007/BF00215721
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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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    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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    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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    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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    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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    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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    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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    Quantitative transient gene expression: Comparison of the promoters for maize polyubiquitin1, rice actin1, maize-derivedEmu andCaMV 35S in cells of barley, maize and tobacco (1994)
    Springer
    Transgenic research 3 (1994), S. 249-255 
    Details
    ISSN: 1573-9368
    Keywords: transient gene expression ; β-glucuronidase ; luciferase ; Hordeum vulgare ; Zea mays ; Nicotiana tabacum ; quantitation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The particle gun approach was used for the quantification of promoter efficiency in a test system for transient gene expression. β-Glucuronidase was used as reporter gene for determining promotote strength. The variability inherent in this gene transfer system was considerably reduced by calculating a transformation efficiency factor given by the expression of a cotransferred second reporter gene (firefly luciferase). The calibration of β-glucuronidase activity by the transformation efficiency factor caused a lower statistical variance of the values and allowed reliable results to be obtained with a smaller set of repetitions. The CaMV 35S promoter (as a control) and the monocot-specific promoters for maize polyubiquitin1, rice actin 1 and the maize-derivedEmu were characterized and compared with respect to expression strength, as tested under identical conditions in suspension cell cultures of maize, barley and tobacco. Compared to the 35S promoter, the monocot-specific promoters show up to 15-fold higher expression in maize and barley but give only weak expression in tobacco. No expression was found for the rice actin 1 promoter in tobacco. The level of reporter gene expression is influenced by the osmotic potential in the agar medium. For theEmu promoter, the calibrated β-glucuronidase activities remained mearly constant at low sucrose concentrations. Above 8% sucrose, the calibrated activities increased steadily with increasing osmotic conditions, reaching a three-to four-fold higher level at the highest sucrose concentration (32%) as compared to the standard concentration (4% sucrose) in the medium.
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    URL: http://dx.doi.org/10.1007/BF02336778
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    Allosteric regulation of the Golgi inosine diphosphatase from corn roots (1994)
    Springer
    Protoplasma 179 (1994), S. 131-141 
    Details
    ISSN: 1615-6102
    Keywords: Inosine diphosphatase ; Golgi membranes ; Zea mays ; Roots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Light microsomes of corn roots, enriched in endoplasmic reticulum and Golgi membranes, have an IDPase activity which is stimulated by Triton X-100 and by cold storage. In the native state, the enzyme activity does not follow Michaelis-Menten kinetics. It hydrolyses IDP with K0.5 of about 900 μM and Vmax of 300–400 nmol Pi/mg protein/min. In the presence of Triton X-100, the enzyme is maximally stimulated and it renders to a Michaelis-Menten behavior with a Km of about 500 μM and a Vmax of 800–1200 nmol Pi/mg protein/min. The maximal effect of the detergent occurs at about 1 mM IDP (270%), being reduced (190%) at high IDP concentrations (〉2 mM) which, per se, have a slight stimulatory effect on the enzyme. On the other hand, we observed that ATP (〉2 mM) and adenosine inhibit the IDPase. The effects of the nucleotides and of the adenosine are abolished in the presence of Triton X-100, which makes the enzyme fully active. Furthermore, we observed that detergent treatment of the membranes reduces the change in the activation energy which occurs at 10 °C and eliminates cooperative effects, as revealed by the Arrhenius analysis and the Hill analysis, respectively. We also observed that IDPase inhibition by ATP is maximal at low IDP concentrations (1 mM), whereas it decreases at high concentrations of IDP (4 mM), which promote maximal velocities in the native enzyme. Conversely, the inhibitory effect of adenosine is not reduced at high IDP concentrations. Pyrophosphate also inhibits the IDPase, but the effect is non-competitive and it is cumulative with that of ATP. We also observed that the latent activity of the IDPase (Triton-stimulated IDPase) is reduced by pre-treatment of the membranes with glutaraldehyde. The results indicate that Golgi IDPase is an allosteric enzyme which is positively modulated by IDP and negatively modulated by ATP and adenosine. Pyrophosphate inhibits the IDPase, but it seems to act at the catalytic site, whereas the other modulators appear to interact with a distinct regulatory site.
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    URL: http://dx.doi.org/10.1007/BF01403951
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    Microtubule organization and morphogenesis of stomata in caffeine-affected seedlings ofZea mays (1991)
    Springer
    Protoplasma 165 (1991), S. 11-26 
    Details
    ISSN: 1615-6102
    Keywords: Zea mays ; Caffeine ; Microtubules ; Wall thickening ; Stomatal pore opening ; Microtubule organizing centres
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Treatment ofZea mays seedlings with a 5 mM caffeine solution inhibits cytokinesis in guard cell mother cells (GMCs), producing unicellular, binucleate aberrant stomata (a-stomata). Ventral wall (VW) strips of limited length, which usually meet the wall portions of GMCs adjoining the cortical zone of the preprophase microtubule band (PMB), are laid down in many a-stomata. In a-stomata with or without VW-strips, the periclinal walls are lined by numerous microtubules (Mts) converging on their mid-region, where local wall thickenings are deposited. When the VW-strips reach the mid-region of the periclinal walls, thickenings lined by numerous Mts rise at their free margins. In certain a-stomata an anticlinal wall column, surrounded by a dense Mt bundle, grows centripetally from either or both of the periclinal wall thickenings. In wall thickenings, the cellulose microfibrils are co-aligned with the adjacent Mts. Pore formation is initiated in all a-stomata. Deposition of an electron dense intra-wall material followed by lysis precedes “pore” opening. This process is closely related to the a-stornata morphogenesis. These observations show that the primary morphogenetic phenomenon in a-stomata is the establishment of an intense and stable polarity in the cytoplasm abutting on the mid-region of the periclinal walls and/or the adjacent plasmalemma area. Prime morphogenetic factor(s), including microtubule organizing centres (MTOCs), seem to function in these sites. Morphogenesis in a-stomata is a Mt-dependent process that is carried out as in normal stomata but in the absence of a VW.
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    URL: http://dx.doi.org/10.1007/BF01322273
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    Mechanosensory microtubule reorientation in the epidermis of maize coleoptiles subjected to bending stress (1994)
    Springer
    Protoplasma 182 (1994), S. 96-101 
    Details
    ISSN: 1615-6102
    Keywords: Auxin ; Mechanical stress ; Mechanosensor ; Microtubule orientation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Plants respond to mechanical stress by adaptive changes in growth. Although this phenomenon is well established, the mechanism of the perception of mechanical forces by plant cells is not yet known. We provide evidence that the cortical microtubules sub-adjacent to the growth-controlling outer epidermal cell wall of maize coleoptiles respond to mechanical extension and compression by rapidly reorientating perpendicular to the direction of the effective force change. These findings shed new light on many seemingly unrelated observations on microtubule reorientation by growth factors such as light or phytohormones. Moreover, our results suggest that microtubules associated with the plasma membrane are causally involved in sensing vectorial forces and provide vectorial information to the cell that can be utilized in the orientation of plant organ expansion.
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    URL: http://dx.doi.org/10.1007/BF01403471
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    The effect of Cr (VI) on different inbred lines ofZea mays (1991)
    Springer
    Protoplasma 162 (1991), S. 12-19 
    Details
    ISSN: 1615-6102
    Keywords: Zea mays ; Chromium ; Roots ; Cell cycle
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Four inbred lines ofZea mays (33.16, B 68, N 7B, B 77) were grown in nutrient solution to which K2Cr2O7 was added to give final concentration of 5 mg/l Cr (VI). The most evident differences in metal tolerance were observed between the B 68 and 33.16 line: in fact, even though the level of Cr (VI) was almost the same in the root tissues of both lines after 6 d of treatment, in the B 68 line, Cr induced marked alterations of nuclear structure and a progressive arrest of the cell cycle in G 1. In the 33.16 line, on the contrary, the integrity of the nuclei was well preserved and the progression of the cell cycle was only barely affected.
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    Improved recovery of (1→3),(1→4)-β-D-glucan synthase activity from Golgi apparatus ofZea mays (L.) using differential flotation centrifugation (1994)
    Springer
    Protoplasma 180 (1994), S. 92-97 
    Details
    ISSN: 1615-6102
    Keywords: Zea mays ; (1→3), (1→4)-β-D-glucan ; Glucan synthase ; Golgi apparatus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The synthesis of (1→3), (1→4)-β-D-glucan (MG) is associated with the Golgi apparatus of maize. Identification of in vitro reaction products by enzymic hydrolysis and separation of diagnostic oligosaccharides by HPLC was used as a specific assay for MG synthase activity. Large quantities of highly enriched membrane are needed to study the enzyme components of MG synthesis. We directly obtained highly enriched Golgi apparatus in a single flotation centrifugation, without the necessity of an initial downward centrifugation. This new procedure has improved the yield of Golgi apparatus, and has improved recovery of MG synthase activity. The substrate in glucan synthase reactions is UDP-Glc, but UDP-Glc is also a substrate in many other reactions, including the production of simple glucosides. In addition, much of the labeled Glc from UDP-Glc is broken down to Glc-1-P and Glc under MG synthase reaction conditions. We have explored some inhibitors of phosphatase, phosphorylase, phosphodiesterase, and glucosidase activities in order to minimize these competing reactions and increase the activity of MG synthase.
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    URL: http://dx.doi.org/10.1007/BF01379227
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    Cytoplasmic calcium levels in protoplasts from the cap and elongation zone of maize roots (1991)
    Springer
    Protoplasma 163 (1991), S. 181-188 
    Details
    ISSN: 1615-6102
    Keywords: Cytoplasmic calcium ; Fura ; Indo ; Protoplasts ; Gravitropism ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Calcium has been implicated as a key component in the signal transduction process of root gravitropism. We measured cytoplasmic free calcium in protoplasts isolated from the elongation zone and cap of primary roots of light-grown, vertically oriented seedlings ofZea mays L. Protoplasts were loaded with the pentapotassium salts of fura-2 and indo-1 by incubation in acidic solutions of these calcium indicators. Loading increased with decreasing pH but the pH dependence was stronger for indo-1 than for fura-2. In the case of fura-2, loading was enhanced only at the lowest pH (4.5) tested. Dyes loaded in this manner were distributed predominantly in the cytoplasm as indicated by fluorescence patterns. As an alternative method of loading, protoplasts were incubated with the acetoxymethylesters of fura-2 and indo-1. Protoplasts loaded by this method exhibited fluorescence both in the cytoplasm and in association with various organelles. Cytoplasmic calcium levels measured using spectrofluorometry, were found to be 160±40 nM and 257±27 nM, respectively, in populations of protoplasts from the root cap and elongation zone. Cytoplasmic free calcium did not increase upon addition of calcium to the incubation medium, indicating that the passive permeability to calcium was low.
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    The quiescent center in roots of maize: initiation, maintenance and role in organization of the root apical meristem (1994)
    Springer
    Protoplasma 183 (1994), S. 100-106 
    Details
    ISSN: 1615-6102
    Keywords: Auxin ; Meristem (root) ; Quiescent center ; Root cap ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Using roots of maize, we tested the hypothesis that the origin and maintenance of the quiescent center (QC) are a consequence of polar auxin supply. Exposing roots to the polar auxin transport inhibitor 2,3,5-triiodobenzoic acid (TIBA), or to low temperature (4 °C, with subsequent return to 24 °C), enhances mitotic frequency within the QC. In both treatments, the QC most typically is activated at its distal face, and the protoderm/dermatogen undergoes several periclinal divisions. As a result, the root body penetrates and ruptures the root cap junction and the characteristic “closed” apical organization changes to “open”. A QC persists during these changes in apical organization, but it is diminished in size. The data from the TIBA-treated roots suggest a role for auxin in the origin and maintenance of the QC, and further, that alterations in QC dimensions are a consequence of polar auxin supply. We hypothesize that the root cap, and specifically the root cap initials, are important in regulating polar auxin movements towards the root apex, and hence are important in determining the status of the QC.
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    Genetic and molecular analysis of Sn, a light-inducible, tissue specific regulatory gene in maize (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 401-410 
    Details
    ISSN: 1617-4623
    Keywords: Flavonoids ; Light regulation ; Sn locus ; Tissue-specificity ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The Sn locus of maize is functionally similar to the R and B loci, in that Sn differentially controls the tissue-specific deposition of anthocyanin pigments in certain seedling and plant cells. We show that Sn shows molecular similarity to the R gene and have used R DNA probes to characterize several Sn alleles. Northern analysis demonstrates that all Sn alleles encode a 2.5 kb transcript, which is expressed in a tissue-specific fashion consistent with the distribution of anthocyanins. Expression of the Sn gene is light-regulated. However, the Sn: bol3 allele allows Sn mRNA transcription to occur in the dark, leading to pigmentation in dark-grown seedlings and cob integuments. We report the isolation of genomic and cDNA clones of the light-independent Sn: bol3 allele. Using Sn cDNA as a probe, the spatial and temporal expression of Sn has been examined. The cell-specific localization of Sn mRNA has been confirmed by in situ hybridization using labelled antisense RNA probes. According to its proposed regulatory role, expression of Sn precedes and, in turn, causes a coordinate and tissue-specific accumulation of mRNA of structural genes for pigment synthesis and deposition, such as A1 and C2. The functional and structural relationship between R, B, Lc and Sn is discussed in terms of an evolutionary derivation from a single ancestral gene which gave rise this diverse gene family by successive duplication events.
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    Molecular analysis of theBg-rbg transposable element system ofZea mays L. (1991)
    Springer
    Molecular genetics and genomics 227 (1991), S. 91-96 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Transposable elements ; Opaque-2 ; Waxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The two components of theBg-rbg transposable element system of maize have been cloned. TheBg element, isolated from the mutable allelewx-m32 :: Bg is inserted in the intron of theWaxy (Wx) gene between exons 12 and 13. The length of the element is of 4869 bp.Bg has 5 by terminal inverted repeats, and generates upon insertion an 8 by direct duplication of the target sequence. Both ends of theBg element contain a 76 by direct repeat adjacent to the terminal inverted repeats. The hexamer motif TATCGkC G is here repeated several times in direct or inverse orientation. Therbg element was isolated from the mutable alleleo2m(r) where it is located in the promoter region of theOpaque-2 (O2) gene.rbg is approximately 4.5 kb in length, has terminal inverted repeats identical to those of theBg element, and is also flanked by an 8 by direct duplication at the target site. LikeBg, rbg carries the 76 by direct repeats. Restriction enzyme analysis reveals that, compared toBg, the receptor element is distinguishable by small deletion and insertion events. Sequence data indicate that not more than 75% homology exists at the DNA level between therbg element and the autonomousBg element.
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    Isolation and characterization of a maize gene encoding chalcone flavonone isomerase (1994)
    Springer
    Molecular genetics and genomics 242 (1994), S. 1-8 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; Flavonoid biosynthesis ; P gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We report here the first cloning of a chalcone flavonone isomerase gene (CHI) from maize. Northern blot experiments indicate that the maize CHI gene (ZmCHI1) is regulated in the pericarp by the P gene, a myb homologue. The ZmCHI1 gene encodes a 24.3 kDa product 55% and 58% identical to CHI-A and CHI-B from Petunia, respectively. This maize CHI gene has four exons and an intron-exon structure identical to the CHI-B gene of Petunia hybrida. RFLP mapping data indicate that some inbred lines contain two additional CHI-homologous sequences, suggesting an organization more complex than that found in Petunia or bean. The possibility that the additional CHI-homologous sequences are responsible for the lack of CHI mutants in maize will be discussed.
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    Direct genetic selection of a maize cDNA for dihydrodipicolinate synthase in an Escherichia coli dapA −auxotroph (1991)
    Springer
    Molecular genetics and genomics 228 (1991), S. 287-293 
    Details
    ISSN: 1617-4623
    Keywords: Lysine biosynthesis ; Feedback regulation ; Zea mays ; Genetic complementation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dihydrodipicolinate synthase (DHPS; EC 4.2.1.52) is the first committed enzyme in the lysine branch of the aspartate-derived amino acid biosynthesis pathway and is common to bacteria and plants. Due to feedback inhibition by lysine, DHPS serves in a regulatory role for this pathway in plant metabolism. To elucidate the molecular genetic characteristics of DHPS, we isolated a putative full-length cDNA clone for maize DHPS by direct genetic selection in an Escherichia coli dapA −auxotroph. The maize DHPS activity expressed in the complemented E. coli auxotroph showed the lysine inhibition characteristics of purified maize DHPS, indicating that the cDNA encoded sequences for both the catalytic function and regulatory properties of the enzyme. The N-terminal amino acid sequence of purified maize DHPS was determined by direct sequencing and showed homology to a sequence within the cDNA, indicating that the clone contained the entire coding region for a mature polypeptide of 326 amino acids plus a 54 amino acid transit peptide sequence. The molecular weight of 35854, predicted from the deduced amino acid sequence, was similar to the 38 000 Mr determined by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) for the purified enzyme from maize. DHPS mRNAs complementary to the cDNA were detected in RNA isolated from developing maize endosperm and embryo tissues. Southern blots indicated the presence of more than one genomic sequence homologous to DHPS per haploid maize genome.
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    Newly activated germinal Uq elements in maize are clustered on one linkage group independently of the standard Uq element (1991)
    Springer
    Molecular genetics and genomics 229 (1991), S. 161-174 
    Details
    ISSN: 1617-4623
    Keywords: Zea mays ; transposable element ; Uq activation ; Uq cluster
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Allelism tests between the standard Uq element (Uq1) and five newly activated germinal Uq elements (Uq2, Uq3, UQ4, Uq5, and Uq6) demonstrate that these new Uq elements are independent of Uq1. Gametes that either contain one Uq or various combinations of two different and phenotypically distinguishable Uq elements, have been constructed either with or without the a-ruq reporter allele. Genetic analyses of the progenies of the gametes (using the standard a-ruq tested line as the other parent) have indicated that (i) each Uq element, when present alone, has the capacity to express full activity except when a secondary transposition or loss of activity has occurred; (ii) all five new Uq elements are independent of Uq1 with respect to transposition activity; and (iii) these newly originated Uqs are clustered on one linkage group. Uq2 is allelic to Uq4, and Uq3 is allelic to Uq5, whereas Uq6 is linked to both allelic pairs. A putative linkage map of these Uq elements is presented. In reciprocal crosses there is a striking difference in phenotypic segregation of Uq; when transmitted via the male parent Uq loses full expression capacity.
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    Intron enhancement of gene expression and the splicing efficiency of introns in maize cells (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 81-93 
    Details
    ISSN: 1617-4623
    Keywords: Enhancement ; Intron ; Splicing ; Transient assay ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The inclusion of the alcohol dehydrogenase 1-S (Adh1-S) intron 1 in the transcription unit of maize gene constructs has been shown to increase gene expression in cultured maize cells. We have extended these studies with Adh1-S intron 1 using the firefly luciferase, Escherichia coli β-glucuronidase and chloramphenicol acetyltransferase reporter genes adjoined to different plant promoters and find enhancement of transient gene expression in all cases but one. We also show that the enhancement phenomenon can be mediated by the third intron of the maize actin gene. In all cases tested, the inclusion of an intron results in increased levels of steady-state RNA. The degree of enhancement depends on the exon sequences flanking the intron; flanking exons also influence the efficiency of intron splicing. Unexpectedly, unspliced RNAs accumulate during the transient assay.
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    Detection and abundance of mRNA and protein encoded by transposable element Activator (Ac) in maize (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 186-192 
    Details
    ISSN: 1617-4623
    Keywords: Transposase ; DNA-binding protein ; Zea mays ; mobile DNA
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The 3.5 kb long mRNA of the maize transposable element Ac contains an open reading frame (ORFa) which encodes a polypeptide of 807 amino acids, the putative transposase of Ac. The Ac mRNA is a rare transcript: we now estimate the fraction of Ac mRNA in wx-m7::Ac seedlings to be 2–13 × 10−5 of the polyA RNA. Assuming that maize cells contain similar amounts of polyA RNA as another monocot (0.16 pg/cell), this is equivalent to 1.5–10 transcripts in each cell. A protein with an apparent molecular weight of 112 kDa is detected, by five antisera directed against different segments of ORFa, exclusively in nuclear extracts from Ac-containing maize. This protein is most likely the full-length Ac ORFa protein. We estimate its concentration to be in the range of 3 × 10− of the nuclear proteins, or about 1000 molecules per triploid endosperm cell containing one Ac element.
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    Sequence-specific interactions of a maize factor with a GC-rich repeat in the phosphoenolpyruvate carboxylase gene (1991)
    Springer
    Molecular genetics and genomics 225 (1991), S. 203-208 
    Details
    ISSN: 1617-4623
    Keywords: Phosphoenolpyruvate carboxylase ; DNA binding protein ; Zea mays ; C4 plant
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A plant nuclear protein PEP-I, which binds specifically to the promoter region of the phosphoenolpyruvate carboxylase (PEPC) gene, was identified. Methylation interference analysis and DNA binding assays using synthetic oligonucleotides revealed that PEP-I binds to GC-rich elements. These elements are directly repeated sequences in the promoter region of the PEPC gene and we have suggested that they may be cis-regulatory element of this gene. The consensus sequence of the element is CCCTCTCCACATCC and the CTCC is essential for binding of PEP-I. PEP-I is present in the nuclear extracts of green leaves, where the PEPC gene is expressed. However, no binding was detected in tissues where the PEPC gene is not expressed in vivo, such as roots or etiolated leaves. Thus, PEP-1 is the first factor identified in plants which has different binding activity in light-grown compared with dark-grown tissue. PEP-I binding is also tissue-specific, suggesting that PEP-1 may function to coordinate PEPC gene expression with respect to light and tissue specificity. This report describes the identification and characterization of the sequences required for PEP-1 binding.
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    Contribution of organic acids to the acidification of the rhizosphere of maize seedlings (1991)
    Springer
    Plant and soil 132 (1991), S. 159-163 
    Details
    ISSN: 1573-5036
    Keywords: enzymatical conversion ; organic-acid secretion ; proton secretion ; rhizosphere ; roots ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The participation of organic acids in the process of soil acidification was related to other H+ pumping processes. The ratio between efflux of organic acids and proton secretion of maize roots was determined with the use of a pH-stat combined with a collecting system for organic acids. Changes in the composition of carboxylic acids influenced by nitrogen supply were monitored by HPLC and via enzymatic conversion. The following substances were found to be secreted by maize roots: glycolate, glyoxylate, fumarate, 2-oxoglutarate and oxalate. Malate, however, could not be detected. There is no organic acid dominantly secreted by the roots, but changes are observed during aging which might result from deficiencies of nutrients e.g. P. Fertilization of N-deficient plants with urea leads to a significant change in the composition of acids secreted. In this case, oxalate was additionally detected with a concomitant increase in glyoxylate, indicating important changes in metabolism. Acidification of the rhizosphere is predominantly maintained by secretion of protons, not by efflux of organic acids, which contributed 0.2 to 0.3% to this process only. The role of organic acids in nutrient uptake is discussed.
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    URL: http://dx.doi.org/10.1007/BF00010396
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    Soil core and minirhizotron comparison for the determination of root length density (1994)
    Springer
    Plant and soil 161 (1994), S. 225-232 
    Details
    ISSN: 1573-5036
    Keywords: minirhizotron ; root-length density ; soil core ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Detailed knowledge of the distribution of roots in the soil is important in understanding the extraction of water and nutrients from soil. Various techniques have been developed to monitor root-length density under field conditions. Excavation techniques, including soil cores, have long been considered to give reliable estimates of root-length density, but these techniques are laborious in sample collection and tedious in determination of root lengths. An attractive alternative for monitoring root-length density has been the minirhizotron whereby a periscope is inserted into a clear tube permanently installed in the soil for repeated and rapid measures of root development. The objective of this study was to compare the ability of the minirhizotron technique to measure root-length density as compared to the root-core technique. As in previous studies, substantial disagreement existed between the two techniques in the top 30-cm of the soil. The results from the minirhizotron consistently indicated a much lower root population than the root-core technique in the surface layer of soil. This is especially worrisome because more than 45% of the root-length density was found in this layer with the root-core technique. At deeper soil layers, the minirhizotron data proved to be no less variable than the root-core technique making the determination of statistically significant results difficult. Finally, the relationship between the minirhizotron and soil-core results varied with time even when the observations from the soil surface layer were ignored. Attempts to directly translate minirhizotron observations into a root-length density using a correlation approach would be suspect based on the results of this experiment.
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    URL: http://dx.doi.org/10.1007/BF00046393
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    Contributions of the surface of the root tip to the growth of Zea roots in soil (1994)
    Springer
    Plant and soil 165 (1994), S. 315-321 
    Details
    ISSN: 1573-5036
    Keywords: cell wal's ; epidermis ; growth ; root development ; soil penetration ; stiffness ; Zea diploperennis ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The development of the epidermal layer of roots of Zea is traced from the quiescent centre to the zone where root hairs develop. In the zone of cell division a three layered coat forms on the outside of the epidermal cells consisting of the outer epidermal walls, overlaid by a two-layered pellicle composed of a thick fibrillar inner layer of polysaccharide, and a thin fibrillar outer layer of protein. The epidermal cells divide several times in the same longitudinal file but rarely across a radius to give a new longitudinal file. Thus, the radial walls become much thicker than all but the original transverse walls, and packets of up to 32 daughter cells derived from a single initial may be distinguished. The pellicle develops during these divisions as a continuum over the outer walls of the daughter cells. It is proposed that the pellicle provides a stiffening to the forward end of the root which permits it to penetrate soil without bending. Support for this hypothesis is shown by the Zea mays mutant Ageotropic in which the pellicle is absent, the epidermal surface is disorganized, and which grows crookedly through soil. In the zone of extension growth of normal roots of two Zea species the pellicle thins and disappears. Circumferential strips of the pellicle were peeled off the young epidermal cells and could be stretched to twice their length. This deformation is partly the result of the pellicle stretching and breaking above the attachments of the radial walls. After normal thinning of the pellicle, detachment of the radial walls at their outer ends produces a corrugated surface in the proximal zone of the root tips. In dicotyledons (e.g., soybean), there is no similar pellicle, but a stiff root tip is produced by a long multi-layered root cap, the proximal portion of which covers the elongating epidermal surface.
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    URL: http://dx.doi.org/10.1007/BF00008075
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    Comparison of selective agents for use with the selectable marker gene bar in maize transformation (1994)
    Springer
    Plant cell, tissue and organ culture 36 (1994), S. 1-7 
    Details
    ISSN: 1573-5044
    Keywords: bialaphos ; glufosinate ; phosphinothricin ; l-proline ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effectiveness of four phosphinothricin (PPT)-based selective agents were evaluated for use in maize transformation: glufosinate, bialaphos, Basta® and Herbiace®. Glufosinate and its commercial formulation, Basta®, were less effective in controlling growth of non-transgenic corn callus than the tripeptide, bialaphos, or its commercial formulation, Herbiace®. Addition of 25 mM l-proline had no significant effect on selection when using bialaphos. However, when l-proline was included with the selective agent glufosinate, selection was inhibited and callus growth was enhanced. At four weeks, callus growth on 0.3, 1.0 and 3.0 mg l-1 glufosinate in the presence of proline was 76, 43, and 21% of control growth, respectively, and in the absence of proline was only 32, 9, and 6% of control growth. Optimized selection protocols for Basta® and bialaphos yielded comparable numbers of transformants. Using these protocols, fertile transgenic plants were regenerated from transformed callus cultures.
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    URL: http://dx.doi.org/10.1007/BF00048308
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    Variation and covariation of silage maize digestibility estimated from digestion trials with sheep (1991)
    Springer
    Euphytica 59 (1991), S. 61-72 
    Details
    ISSN: 1573-5060
    Keywords: Breeding ; heritability ; in vitro digestibility ; in vivo digestibility ; maize ; silage maize ; variation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Variation and covariation for agronomic and digestibility traits of silage maize are reported from a compilation of 22 years of experiments with standard sheep. Genotype effects of DOM and DCF were highly significant, even when genotypes were nested in earliness groups or brown-midrib hybrids discarded (Table 2). The genetic variance of crude fiber content was low, but the variance of the DCF was high. The genetic variance of DOM was about 4 times lower than genetic variance of DCF, but broad sense heritability of DOM was higher because of lower residual variance (Table 3). Genetic correlations between grain or crude fiber content and DOM had similar absolute values, 0.65, so each of these two traits was an important but not the unique determinant of silage maize quality. There was no correlation between DCF and grain or crude fiber content. Yield was not related to DOM or DCF within each group of earliness, allowing some quality improvement without agronomic drift (Table 4). Except for late hybrids, most of DOM differences between groups of earliness came from lowering of minimum value, while maximum values were similar. It was the contrary for DCF, with similar minimum values for all groups (Table 5). There was no obvious correlation between year of registration of hybrids and DOM or DCF, but extra new variation seemed obtained only for low values (Figs 1, 2; Table 6). IVDOM according to the APC process was a poor predictor of DOM, especially when brown-midrib hybrids and earliness effects were discarded; but because heritability of this trait was similar to DOM heritability, such enzymatic processes could probably be used to avoid drift towards poor DOM with hybrids bred for higher stalk strength.
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    URL: http://dx.doi.org/10.1007/BF00025362
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    Genetic and environmental effects on abscisic acid accumulation in leaves of field-grown maize (1994)
    Springer
    Euphytica 78 (1994), S. 81-89 
    Details
    ISSN: 1573-5060
    Keywords: abscisic acid ; inheritance ; drought stress ; Zea mays ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary This study analyzes the components of phenotypic variation for abscisic acid (ABA) content in maize (Zea mays L.) leaves and the correlations with drought sensitivity index (DSI) and silk delay (SD), involved in the reaction to water deficit. Eight early- and seven medium-maturity inbreds were examined in field trials: in 1990 with low irrigation volume and in 1991 with low and high irrigation volumes. ABA concentration and DSI were investigated at growth stages (S) corresponding to stem elongation (S3), appearance of the first husks (S4), and mid-end of silking (S5). The ABA concentration was significantly higher in conditions of water deficit and in the later growth stage. The genetic component for ABA concentration attained higher relative values than those shown by DSI in the same growth stages and by SD; moreover, it increased from growth stage 3 to stage 5. The genotype × year and genotype × irrigation volume interactions were smaller for ABA concentration than for DSI and SD. The broad sense heritability on a plant basis, estimated in drought conditions, for ABA concentration ranged from 21.4 to 55.1% according to maturity group and growth stage. A wide variation was observed among lines for ABA concentration: the medium-maturity group showed a three-fold range (from 219 to 605 ng ABA g−1 dry weight). No clear relationships between ABA concentration, DSI and SD were found. These results indicate the feasibility of a selection for ABA concentration within segregating populations derived from crosses between the inbred lines herein tested.
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    URL: http://dx.doi.org/10.1007/BF00021401
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    Breeding for yield and nutritive value in forage maize: An easy criterion for stover quality, and genetic analysis of Lancaster variety (1991)
    Springer
    Euphytica 53 (1991), S. 61-66 
    Details
    ISSN: 1573-5060
    Keywords: Zea mays ; forage maize ; stover ; nutritive value ; heritability ; quantitative inheritance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The maize populations BS13 (S2) C4 and Lancaster are compared with respect to their potential as forage maize. In light of the preliminary results, the Lancaster population was chosen for a more thorough study. The determination of NDF gave a sufficiently precise estimate of the stover digestibility within our experimental conditions. The heritability of stover and grain production was 0.59 and 0.30, respectively, whilst that of the stover NDF was 0.32. The additive genetic correlation between NDF and stover production, possibly attributable to the architecture of the plant, favours the selection of genotypes that produce more and better forage.
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    URL: http://dx.doi.org/10.1007/BF00032034
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    Effects of high temperatures on mature pollen grains in wild and cultivated maize accessions (1991)
    Springer
    Euphytica 55 (1991), S. 203-207 
    Details
    ISSN: 1573-5060
    Keywords: Zea mays ; maize accessions ; teosinte ; mature pollen ; heat tolerance ; pollen tube length ; pollen viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The effects of high temperature on mature pollen of various maize lines were investigated. Genotypic differences in pollen reaction to high temperature were revealed. Pollen grains resistant to high temperature (35°C, 26°C) were characterized by higher germination capacity and better ability to develop normal pollen tubes. The studies are of interest to evaluate reproductive system tolerance and conduct gamete selection at the mature pollen grain stage in maize.
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    URL: http://dx.doi.org/10.1007/BF00021240
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    Chemical induction of apomictic seed formation in maize (1991)
    Springer
    Euphytica 56 (1991), S. 97-105 
    Details
    ISSN: 1573-5060
    Keywords: growth regulators ; dimethyl sulfoxide ; Zea mays ; apomixis ; chemical induction ; maize seed set
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Silks of 18 maize (Zea may L.) F1 hybrids were treated with different combinations of 9 growth regulators, colchicine, and dimethyl sulfoxide (DMSO) for the purpose to induce apomixis (agamospermy) in 1988 and 1989. Hybrid K301 × K303 gave the highest (0.36%) average frequency of seed induction among the hybrids. The most effective treatments were DMSO, gibberellic acid plus 6-benzyl aminopurine (6-BA), and DMSO plus methanesulfonic acid. Individually, the highest frequency of seed induction was 1.4% for hybrid K731×K306 when treated with α-naphthalene acetic acid (NAA)-zeatin mixture. The frequency of seed induction seemed to depend partially on the interaction between chemicals and hybrids. Cytological observation of root-tip cells indicated that the majority of the seeds obtained were diploid, some were mixoploid, and a few were haploid. Diploid plants from induced seeds from the same parent were morphologically uniform and resembled the parent. Variations in plant and ear heights were comparable to those of the hybrid parent. Cytological and morphological investigations suggested that the chemically induced seeds originated mainly from somatic tissue but occasionally came from reduced cells in the embryo sac, leading to haploids. The results showed that chemical induction of adventitious embryony in maize hybrids is possible, but the more effective chemicals, their concentrations, and ways of application for increasing the frequency of seed induction need to be explored for practical use.
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    URL: http://dx.doi.org/10.1007/BF00042052
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    Analysis of light-induced reduction of the photochemical capacity in field-grown plants. Evidence for photoinhibition? (1991)
    Springer
    Photosynthesis research 27 (1991), S. 31-39 
    Details
    ISSN: 1573-5079
    Keywords: chlorophyll fluorescence induction ; field studies ; Helianthus annuus ; Phaseolus vulgaris ; photoinhibition ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract It was tested whether field-grown plants (Phaseolus vulgaris, Zea mays and Helianthus annuus) reflect photoinhibitory effects under natural conditions. Attached leaves were used for determination of the photochemical capacity of Photosystem II (Fv/Fm) by means of a portable fluorimeter (PSM, BioMonitor, S.). For a more qualitative description of Fv/Fm, the modifications of the absolute values F0, Fm as well as of the half-rise time of Fm (T/2) were also considered. By comparing artificially shaded and ‘sun exposed’ plants, the direct influence of light on the photochemical capacity was investigated. Under low natural light conditions the differences of the photochemical capacity between shaded and ‘sun exposed’ leaves were negligible in all three species. On a day with full sunlight a decline of Fv/Fm was observable at noon-time in the ‘sun exposed’ leaves of all three species, although the absolute values differed between the species compared. Additionally, the extent of the recovery of Fv/Fm was varying. Both phenomena could be due to differences in the photosynthetic apparatus (e.g., C3−C4, ontogenetic stage, sun-shade type), to self-shading phenomena (comparing leaf layers of Zea and Helianthus) or to differences in the activity of repair mechanisms possibly caused by other environmental factors (vapour pressure deficit = VPD, drought and temperature phenomena). Nevertheless, the results of the shading experiments and the comparison of species lead to the conclusion that primarily light-induced reduction of the photochemical capacity appears at noon in leaves exposed to full sunlight, a partial restoration of Fv/Fm takes place till the evening. Artifically shaded plants show only a slight alteration of the photochemical capacity.
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    URL: http://dx.doi.org/10.1007/BF00029974
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    Endomycorrhizal fungal species mediate 15N transfer from soybean to maize in non-fumigated soil (1991)
    Springer
    Plant and soil 138 (1991), S. 41-47 
    Details
    ISSN: 1573-5036
    Keywords: fumigation ; Glomus intraradices ; G. vesiculiferum ; G. versiforme ; Glycine max, grass-legume mixture ; 15N ; nitrogen transfer ; soil microorganisms ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effect of mycorrhizal inoculation on 15N transfer from soybean to maize was studied in fumigated and non-fumigated soil. Three Glomus species and a non-inoculated control were compared. In spite of higher levels of root colonization and more abundant hyphae associated with plants growing in fumigated soil, mycorrhizae-enhanced 15N transfer to maize was significant only in non-fumigated plots. High 15N transfer was not only associated with high mycelium density in soil but also with low soil microbial carbon, suggesting that the effect of mycorrhizal fungi on soil microbial populations may be an important factor affecting N transfer between mycorrhizal plants.
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    URL: http://dx.doi.org/10.1007/BF00011806
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    Root movements: Towards an understanding through attempts to model the processes involved (1994)
    Springer
    Plant and soil 165 (1994), S. 293-300 
    Details
    ISSN: 1573-5036
    Keywords: gravitropism ; living systems theory ; nutation ; Phleum pratense L. ; simulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Roots have the ability to change the direction of their forward growth. Sometimes these directional changes are rapid, as in mutations, or they are slower, as in tropisms. The gravitational force is always present and roots have an efficient graviperception mechanism which enables them to initiate gravitropic movements. In trying to model and simulate the course of gravitropic root movements with a view to analyse the component processes, the following aspects of the plant's interaction with gravity have been considered: (1) The level of organization (organism, organ, cell) at which the movement process is expressed; (2) whether the gravity stimulation event is dynamic or static (i.e. whether or not physiologically significant displacements take place with respect to the gravity vector); (3) the sub-systems involved in movement and the processes which they regulate; (4) the mathematical characterization of the relevant sub-systems. A further allied topic is the nature of nutational movements and whether they are linked with gravitropic movements in some way. In considering how they can best be modelled, two types of nutational movements are proponed: stochastic nutation and circumnutation. Most, if not all, natural movements developed in response to static gravistimulation can be viewed as gravimorphisms. This applies at the levels of cell, organ and organism. However, when a system at any one of these levels experiences dynamic gravistimulation, because of its inherent homeostatic properties, it is induced to regenerate a state similar to that previously held. Thus, gravitropism is a regenerative gravimorphic process at the level of the organ.
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    Root growth and nitrate utilization of maize cultivars under field conditions (1994)
    Springer
    Plant and soil 163 (1994), S. 267-277 
    Details
    ISSN: 1573-5036
    Keywords: cultivar ; critical root length density ; field experiment ; nitrate ; N utilization ; root growth ; uptake rate ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In a 2-year field study conducted on a high fertilized Gleyic Luvisol in Stuttgart-Hohenheim significant differences among 10 maize cultivars were observed in soil nitrate depletion. The different capability of the cultivars to utilize nitrate particularly from the subsoil was positively correlated with (a) shoot N uptake at maturity, and (b) root length density (Lv) in the subsoil layers at silking. “Critical root length densities” for nitrate uptake were estimated by (a) calculating uptake rates per unit root length (U), (b) subsequent calculation of needed nitrate concentration in soil solution (C1) to sustain calculated U according to the Baldwin formula, and (c) reducing measured Lv and proportionate increase of U until needed concentration equaled measured concentration. Uptake rate generally increased with soil depth. “Critical root length densities” for cultivar Brummi (high measured root length densities and soil nitrate depletion) at 60–90 cm depth ranged from 7 % (generative growth) to 28 % (vegetative growth) of measured Lv Measured root length density of each other cultivar was higher than “critical root length density” for Brummi indicating that the root system of each cultivar examined would have been able to ensure N uptake of Brummi. Positive relationships between root length density and nitrate utilization as indicated by correlation analysis therefore could not be explained by model calculations. This might be due to simplifying assumptions made in the model, which are in contrast to non-ideal uptake conditions in the field, namely irregular distribution of roots and nitrate in the soil, limited root/soil contact, and differences between root zones in uptake activity. It is concluded from the field experiment that growing of cultivars selected for high N uptake-capacity of the shoots combined with “high” root length densities in the subsoil may improve the utilization of a high soil nitrate supply.
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    Ultrastructural responses of root caps to the herbicides chlorsulfuron and metsulfuron methyl (1994)
    Springer
    Plant and soil 167 (1994), S. 127-134 
    Details
    ISSN: 1573-5036
    Keywords: herbicides ; chlorsulfuron ; metsulfuron methyl ; root cap ultrastructure ; root growth ; Pisum sativum ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Herbicide residues may affect seedlings during early stages of their development. We studied this possibility by the use of light and electron microscopy after incubation of germinating seeds ofPisum sativum L. andZea mays L. with different concentrations of chlorsulfuron and metsulfuron-methyl. By in vitro experiments, we have shown that both herbicides caused growth reduction of the very young roots, and severe ultrastructural alterations and injuries of the root caps of both species. Chlorsulfuron caused increase of electron-dense material in the vacuoles, cytoplasmic degeneration even in the inner secretory cell layers of the cap, and disruption of the amyloplast envelopes with release of the statolithic starch grains. In the initial cell complex of the root cap, the herbicides caused the formation of large concentric aggregates of the rough ER and wall disformations in the cells adjacent to this complex. Scanning electron microscopic observations revealed a decrease of the slime layer ensheathing the root cap and the subapical root surface. We conclude that even in early stages of seed germination, both herbicides seriously affect the gravity perception centre (consisting of the statocytes), and the secretory tissue of the root caps, thus probably disturbing the processes of gravitropism and the protective slime secretion of the roots.
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    Genetic variation for traits relating to nitrogen content of maize stalks (1991)
    Springer
    Euphytica 52 (1991), S. 91-98 
    Details
    ISSN: 1573-5060
    Keywords: Zea mays ; maize ; genetic variation ; nitrate accumulation ; N use efficiency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The objective of this research was to obtain information about expression of genes controlling N concentration in the lower stalk internodes of maize at silking stages and in two other stages during the grain filling period. The inheritance of nitrate-N concentration, total N concentration, and the nitrate-N/total N ratio in the lower stalk internodes was measured in an eight-line diallel cross experiment and in an experiment involving segregating generations. The results show that the parameters examined, particularly nitrate-N concentration, are genetically controlled and that maize plants differ in this respect. Moreover, the magnitude of the general combining ability effects in relation to the size of specific combining ability obtained from the diallel analysis and the mean squares of the analysis of variance of generation means indicated additive heritability of nitrate-N concentration and other N-related traits in maize stalks. These findings suggest to us that a cyclic selection program in maize should be effective in modifying the level of N-related traits concentration in the stalks.
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    URL: http://dx.doi.org/10.1007/BF00021320
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    Evaluation of environments for preliminary testing of maize for yield and stover digestibility (1991)
    Springer
    Euphytica 54 (1991), S. 19-26 
    Details
    ISSN: 1573-5060
    Keywords: Zea mays ; maize ; prediction ability ; discrimination ability ; yield ; digestibility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary The identification of environments suitable for selection should enable plant breeders to test reliably a larger number of genotypes with given resources. This research was undertaken to evaluate discrimination ability (DA) and prediction ability (PA) of eight environments involving two locations. Eckartsweier (Eck) 1 and Voelkenrode (Voe); 2 yer. 1984 (84) and 1985 (85); and two harvests, silage harvest (I) and later (II). It was based on dry matter yield of plant (PDMY), ear (EDMY) and stover (SDMY) and on in vitro digestible organic matter (IVDOM), neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) of stover of 12 inbred lines and their 66 diallel crosses in maize (Zea mays L.). Linear regression coefficient of the performance of genotypes in an environment on that averaged across all environments and its degree of determination were used as measures of the DA and PA of environments, respectively. In hybrids, the DA of environments differed significantly for all traits except SDMY and ADL. Environment Eck851 showed better PA (≥0.63) than other environments for PDMY, EDMY, IVDOM, NDF, and ADF. Among the 12 two-environment combinations. EckI was a better predictor for PDMY, EDMY, IVDOM and NDF (PA≥0.80). The more productive environments showed better DA and PA for PDMY and FDMY than less productive ones. For IVDOM and NDF the first harvest provided better discrimination and prediction than the second harvest. In inbred lines the DA of environments differed significantly for EDMY only. In the present study, PA and DA seemed to be functions of the environments, PA was improved by combining two environments, and some environments seemed to be suitable for preliminary selection of genotypes for such diverse traits as yield and digestibility.
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    Simultaneous gas exchange and fluorescence measurements indicate differences in the response of sunflower, bean and maize to water stress (1991)
    Springer
    Photosynthesis research 27 (1991), S. 189-197 
    Details
    ISSN: 1573-5079
    Keywords: drought ; fluorescence quenching ; gas exchange ; Helianthus annuus ; patchiness ; Phaseolus vulgaris ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Gas exchange and fluorescence measurements of attached leaves of water stressed bean, sunflower and maize plants were carried out at two light intensities (250 μmol quanta m-2s-1 and 850 μmol quanta m-2s-1). Besides the restriction of transpiration and CO2 uptake, the dissipation of excess light energy was clearly reflected in the light and dark reactions of photosynthesis under stress conditions. Bean and maize plants preferentially use non-photochemical quenching for light energy dissipation. In sunflower plants, excess light energy gave rise to photochemical quenching. Autoradiography of leaves after photosynthesis in 14CO2 demonstrated the occurrence of leaf patchiness in sunflower and maize but not in bean. The contribution of CO2 recycling within the leaves to energy dissipation was investigated by studies in 2.5% oxygen to suppress photorespiration. The participation of different energy dissipating mechanisms to quanta comsumption on agriculturally relevant species is discussed.
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    URL: http://dx.doi.org/10.1007/BF00035840
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  • 70
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    Light differentially regulates lateral and longitudinal auxin transport in the mesocotyl of etiolated maize seedlings (1994)
    Springer
    Plant growth regulation 14 (1994), S. 167-171 
    Details
    ISSN: 1573-5087
    Keywords: auxin-transport ; indoleacetic acid ; maize ; photoinhibition ; transport ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The uptake of IAA into excised mesocotyls of non-irradiated maize seedlings was linear up to a concentration of about 4×M and in this range there was a tight coupling between the IAA in the stele and the cortex. Prior irradiation with white light of intact seedlings unbalanced this coupling. Lateral and longitudinal transport were affected differently. In the stele, the effect of prior irradiation on longitudinal transport was multiphasic, with an initial stimulatory effect followed by a negative effect at longer prior irradiation times. The lateral transport from the stele to the cortex showed no stimulatory effect and appeared to be inhibited within at least 15 min. The effect of the prior irradiation on longitudinal transport in the stele appeared to be a high intensity effect. In contrast, the effect of the prior irradiation on the lateral transport from the stele to the cortex was saturated at much lower intensities. The data suggest that the light induced change in the lateral transport of IAA between the two tissues may be due to changes either in the number of open lateral transport channels/carriers or in the conductivity of these channels/carriers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00025219
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  • 71
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    Long-chain free fatty acids: Semiochemicals for host location by western corn rootworm larvae (1994)
    Springer
    Journal of chemical ecology 20 (1994), S. 3335-3344 
    Details
    ISSN: 1573-1561
    Keywords: Diabrotica virgifera virgifera ; fatty acids ; linoleic acid ; oleic acid ; stearic acid ; semiochemical ; attractants ; western corn rootworm ; host location ; Coleoptera ; Chrysomelidae ; Zea mays ; kairomone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract A bioassay-driven sequential fractionation scheme was used to isolate fractions of a crude dichloromethane maize seedling extract behaviorally active to larvae of the western corn rootworm,Diabrotica virgifera virgifera LeConte. (Z,Z)-9,12-Octadecadienoic (linoleic) acid, (Z)-9-octadecenoic (oleic) acid, and octadecanoic (stearic) acid were identified from a purified fraction of maize extract that was attractive to western corn rootworm larvae in choice tests with equal levels of carbon dioxide on both sides of the choice. When synthetic linoleic, oleic, and stearic acids were tested together in the amounts and proportions found in the attractive fraction (1000, 800, and 300 ng of linoleic, oleic, and stearic acids, respectively), significantly more western corn rootworm larvae were found on the side with synthetic free fatty acids plus carbon dioxide than on the side with carbon dioxide alone. Results of the choice-test bioassays were not significantly different when the synthetic blend of free fatty acids was substituted for the purified maize fraction. Neither the purified extract nor the synthetic blend was behaviorally active in preliminary single-choice experiments without carbon dioxide. Linoleic, oleic, and stearic acids were also tested individually in the choice test bioassay with carbon dioxide on both sides of the choice to determine a dose-response curve. Linoleic and oleic acid each had one dose that was significantly attractive in conjunction with carbon dioxide on both sides of the choice, but stearic acid was not active in the doses tested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02033730
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  • 72
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    Relationships among American and Spanish populations of maize (1994)
    Springer
    Euphytica 79 (1994), S. 149-161 
    Details
    ISSN: 1573-5060
    Keywords: maize ; germplasm ; cluster analysis ; landraces ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two experiments were carried out with two objectives. First, to establish the phenetic relationships among the maize (Zea mays L.) landraces from Galicia (Northwestern Spain) maintained at the Misión Biológica de Galicia. Second, to assess the resemblance between a collection of Spanish populations (including the landraces from Galicia) and a set of US Corn Belt varieties. For the first objective 73 varieties from Galicia, along with 9 hybrid checks, were grown in 9×9 simple lattices at two locations for two years. For the second objective 131 populations from the US Corn Belt and Spain, along with 9 hybrid checks, were grown for three years in unreplicated experiments. Cluster analyses were carried out with the first principal components that accounted for a significant amount of the total variation. Four groups were found among the landraces from Galicia. The populations from Spain and America were classified as belonging to nine main groups. The replicated experiment was more accurate than the unreplicated one. However, it is concluded that an unreplicated test grown in several environments is accurate enough to detect the main groups, although some inaccuracies should be expected.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023586
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  • 73
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    Genetic variation for resistance to low-temperature photoinhibition of photosynthesis in maize (Zea mays L.) (1994)
    Springer
    Euphytica 80 (1994), S. 85-93 
    Details
    ISSN: 1573-5060
    Keywords: maize ; Zea mays ; photoinhibition ; photosynthesis ; low-temperature adaptation ; breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Sixty-seven inbred lines of maize were evaluated for resistance to low-temperature photoinhibition of photosynthesis, using a pulse-modulated chlorophyll fluorescence technique. The evaluation procedure was based on leaf discs, which were exposed to a high irradiance (1000 µmol/m2/s) at 7°C. The efficiency of open PSII reaction centres as a reflection of overall photosynthesis was measured before and after a photoinhibition-inducing treatment. Exposure of leaf discs to photoinhibitory condition for 2, 4, and 8 hours resulted in an efficiency reduction of 30, 53 and 83%, respectively. Testing of inbred lines showed large differences for photoinhibition susceptibility. The difference in photosynthetic efficiency between the most extreme lines after a treatment of eight hours was 39%. Resistance to photoinhibition was shown to be relevant under cool field conditions. It proved to be a trait strongly amenable to selection.
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    URL: http://dx.doi.org/10.1007/BF00039302
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  • 74
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    Interaction of analogues of substrate with NADP-malic enzyme from maize leaves (1994)
    Springer
    Photosynthesis research 39 (1994), S. 67-73 
    Details
    ISSN: 1573-5079
    Keywords: Zea mays ; C4-photosynthesis ; decarboxylation ; NADP-ME type ; l-malate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of structural analogues of l-malate was studied on NADP-malic enzyme purified from Zea mays L. leaves. Among the compounds tested, the organic acids behaved as more potent inhibitors at pH 7.0 than at pH 8.0, suggesting that the dimeric form was more susceptible to the inhibition than the tetrameric form of the enzyme. Oxalate, ketomalonate, hydroxymalonate, malonate, oxaloacetate, tartrate, α-hydroxybutyrate, α-ketobutyrate, α-ketoglutarate and α-hydroxyglutarate exhibited linear competitive inhibition with respect to the substrate l-malate at pH 8.0. On the other hand, glyoxylate and glycolate turned out to be non-competitive inhibitors, while glycolaldehyde, succinate, fumarate, maleate and β- and γ-hydroxybutyrate had no effect on the enzyme activity, at the concentrations assayed. These results suggest that the extent of inhibition was dependent on the size of the analogues and that the presence of an 1-carboxyl group along with a 2-hydroxyl or 2-keto group was important for binding of the substrate analogue to the enzyme.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027144
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  • 75
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    Rotation of maize with cowpea improves yield and nutrient use of maize compared to maize monocropping in an alfisol in the northern Guinea Savanna of Ghana (1994)
    Springer
    Plant and soil 160 (1994), S. 171-183 
    Details
    ISSN: 1573-5036
    Keywords: allelopathy ; crop rotation ; nitrogen utilization ; root growth ; soil nitrate depletion ; Vigna unguiculata ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In the northern Guinea Savanna of Ghana (1984–1987) a field experiment was conducted to study the reasons for beneficial effects of rotating maize (Zea mays) and cowpea (Vigna unguiculata) on yield and N and P use of maize. The treatments included two cropping systems, maize monocropping and maize/cowpea rotation, two levels of nitrogen (0 and 80 kg N ha-1 as urea) and two levels of phosphorus application (0 and 60 kg ha-1 P as Volta phosphate rock). Yields and nutrient accumulation of maize were larger in rotation than in monocropping, independent of the N and P level. Fertilizer application (N and P) increased yields of maize in both cropping systems to the same extent. Nitrate contents of the soil after cowpea and after maize monoculture were comparable at the beginning of the cropping period. Also, potential nitrogen mineralization was only slightly larger after cowpea in the unfertilized plots. However, soil nitrate of fertilized plots was similar or even higher under monocropping than under crop rotation, especially in deeper soil layers and at the end of the cropping period. This indicates that in addition to the availability of mineral N, its use by the plants was limiting for the productivity of maize. Root length densities of maize were significant lower in monocropped maize than in maize grown in rotation. Soil physical parameters (infiltration, bulk density, aggregate stability and water capacity) showed a significant deterioration compared to a bush fallow plot, but differed only slightly between the cropping systems. Also in a pot experiment maize growth was much better in the soil from the crop rotation than from the monocropping plots, provided P was eliminated as the main growth-limiting factor. Since this effect persisted in spite of N application and optimization of soil physical properties by mixing the soil with polystyrol it is concluded that the results indicate that yield decline in maize monocropping might be due to allelopathic effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00010143
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  • 76
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    Carbon translocation to the rhizosphere of maize and wheat and influence on the turnover of native soil organic matter at different soil nitrogen levels (1994)
    Springer
    Plant and soil 161 (1994), S. 233-240 
    Details
    ISSN: 1573-5036
    Keywords: C distribution ; native soil organic matter ; rhizosphere ; root released carbon ; wheat ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Wheat and maize were grown in a growth chamber with the atmospheric CO2 continuously labelled with 14C to study the translocation of assimilated carbon to the rhizosphere. Two different N levels in soil were applied. In maize 26–34% of the net assimilated 14C was translocated below ground, while in wheat higher values (40–58%) were found. However, due to the much higher shoot production in maize the total amount of carbon translocated below ground was similar to that of wheat. At high N relatively more of the C that was translocated to the root, was released into the soil due to increased root respiration and/or root exudation and subsequent microbial utilization and respiration. The evolution rate of unlabelled CO2 from the native soil organic matter decreased after about 25 days when wheat was grown at high N as compared to low N. This negative effect of high N in soil was not observed with maize.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00046394
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    Properties of maternal haploid maize plants and potential application to maize breeding (1994)
    Springer
    Euphytica 79 (1994), S. 13-18 
    Details
    ISSN: 1573-5060
    Keywords: Zea mays ; haploid induction ; maternal haploids ; inducer line ZMS ; maize
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Presented are the results of a two-year study of haploid maize plants in the field. The haploids were produced with the aid of inducer line ZMS. In total, 604 and 1030 haploids were obtained and studied in the first and second years, respectively. Tassels of haploid plants were found to be almost completley sterile. Fertility of ears was studied by pollinating them with the pollen from diploid inbred lines, the cross resulting in almost all of the haploid ears carrying kernels. On average 27.4 kernels per ear of haploid plant were obtained in the first year of study and 26.3 in the second. These gave rise to normal diploid plants. This property allows genotypes selected at the level of haploid plants to be involved in breeding process. Unusual plants were found among haploids, phenotypically resembling homozygous lines. It was assumed that the plants had resulted from spontaneous chromosome doubling in haploids. The results of comparative studies of progenies of unusual plants and inbred lines derived from the same synthetic population are presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00023571
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  • 78
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    Calcium-dependent asymmetric movement of 3H-indole-3-acetic acid across gravistimulated isolated root caps of maize (1994)
    Springer
    Plant growth regulation 14 (1994), S. 235-242 
    Details
    ISSN: 1573-5087
    Keywords: auxin transport ; calcium ; gravitropism ; root cap ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract There is evidence that the cap is the initial site of lateral auxin redistribution during the gravitropic response of roots. We tested this further by comparing asymmetric auxin redistribution across the tips of gravistimulated intact roots, decapped roots, isolated root caps and isolated apical sections taken from decapped roots. Gravistimulation caused asymmetric (downward) auxin movement across the tips of intact roots and isolated root caps but not across the tips of decapped roots or across isolated apical root segments. Naphthylphthalamic acid and pyrenoylbenzoic acid, inhibitors of polar auxin transport, inhibited asymmetric auxin redistribution across gravistimulated isolated root caps and across the tips of gravistimulated intact roots. For intact roots there was a positive correlation between the extent of inhibition of assymmetric auxin redistribution by polar auxin transport inhibitors and the extent of inhibition of asymmetric calcium chelating agent, ethylene glycol-bis(β-aminoethyl ether)-N,N,N′,N′-tetraacetic acid, also caused parallel inhibition of asymmetric auxin redistribution and gravitropic curvature and this effect was reversed by subsequent treatment with calcium. The results support the hypothesis that the cap is a site of early development of auxin asymmetry in gravistimulated roots and that calcium plays an important role in the development of lateral auxin redistribution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00024798
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