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  • Zea mays  (92)
  • Wheat  (89)
  • Springer  (181)
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  • 1
    Electronic Resource
    Electronic Resource
    RNA and protein synthesis in sperm cells isolated from Zea mays L. pollen (1993)
    Springer
    Sexual plant reproduction 6 (1993), S. 239-243 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Sperm cell ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Sperm cells are thought to be quiescent in pollen and activated upon pollen germination. To test this hypothesis, protein, RNA and DNA synthesis were assessed in Zea mays sperm cells at different times after isolation from pollen. Protein synthesis changed with time; while some proteins were found to be constitutive in both 0 and 24 h cells, others were synthesized and some disappeared. Overall, the number of proteins detected at 24 h doubled compared with freshly isolated cells. Incorporation of [3H]leucine in 24 h cells was about 50 times that in freshly isolated cells, and that of [5, 6-3H]uridine, about 7 times. Very low incorporation of [6-3H]thymidine into the cells was detected; there was no difference between freshly isolated and 24 h cells. It is possible that the differences in synthetic activity between freshly isolated and 24-h-old cells might correspond to sperm cell activation during pollen tube growth. If so, these metabolic changes may play an important role in fertilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231900
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  • 2
    Electronic Resource
    Electronic Resource
    Genomic mapping of defense response genes in wheat (1999)
    Springer
    Theoretical and applied genetics 98 (1999), S. 226-233 
    Details
    ISSN: 1432-2242
    Keywords: Key words Molecular mapping ; Wheat ; Resistance ; Defense response genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Defense response (DR) genes are a broad class involved in plant defense. In this study we mapped 36 probes representing seven classes of defense response genes. This collection of probes represents genes involved in the hypersensitive response (HR), pathogenesis-related (PR) genes, genes for the flavonoid metabolic pathway, genes encoding proline/glycine-rich proteins, ion channel regulators, lipoxygenase, lectin, and others. Using nullisomic-tetrasomic lines of ‘Chinese Spring’, we were able to assign at least 167 loci to the 21 chromosomes of wheat. Homoeologous group 7 chromosomes possessed the most DR loci followed by group 2. Sixty-two loci were placed on existing genetic linkage maps of wheat. Map locations indicated that the DR gene loci are not randomly distributed throughout the wheat genome, but rather are located in clusters and/or in distal gene-rich regions of the chromosomes. Knowledge of the chromosomal locations and genome organization of DR genes will be useful for candidate gene analysis of quantitative trait loci.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220051062
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  • 3
    Electronic Resource
    Electronic Resource
    Variation in resistance of Mexican landraces of maize to maize weevil Sitophilus zeamais, in relation to taxonomic and biochemical parameters (1993)
    Springer
    Euphytica 74 (1993), S. 227-236 
    Details
    ISSN: 1573-5060
    Keywords: resistance ; taxonomy ; maize ; maize weevil ; indigenous landraces ; phenolic acids ; life history components ; indirect selection ; Zea mays ; Sitophilus zeamais
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Accessions representing twenty eight landraces of maize were assessed for susceptibility to the maize weevil, Sitophilus zeamais in standardized resistance tests. Susceptibility parameters such as weight loss of grain, number of insect progeny produced, the Dobie index of susceptibility, and oviposition on grain were found to vary significantly by genotype, with exceptional resistance found in accessions representing the Naltel, Chapalote and Palomero landraces. As in improved genotypes, susceptibility was negatively correlated to phenolic and protein content of the variety tested but positively correlated to moisture content. A detailed analysis of the phenolics revealed the presence of diferulate which may contribute to mechanical resistance of the seed by cross-linking of cell wall hemicelluloses. A canonical discriminant analysis of the resistance data suggests that most of the five landrace groupings are significantly different. The ancient indigenous and prehistoric mestisos groupings are sources of resistant genotypes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00040405
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  • 4
    Electronic Resource
    Electronic Resource
    Transient expression of GUS and anthocyanin constructs in intact maize immature embryos following electroporation (1993)
    Springer
    Plant cell, tissue and organ culture 33 (1993), S. 195-201 
    Details
    ISSN: 1573-5044
    Keywords: DNA delivery ; electroporation electrolyte ; heat shock ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Electroporation was used for the delivery and subsequent expression of GUS and anthocyanin reporter genes into intact maize immature embryos. The optimal conditions consisted of culturing immature embryos for 4 days on N6 1-100-25-Ag medium prior to electroporation (375 V/cm; 960 µF capacitance) in EPR buffer containing DNA and 0.07 M sodium glutamate at room temperature (22°C) after a 10 min heat shock at 37°C. Under these conditions, over 40 spots of GUS transient activity were observed per immature embryo. Transient gene expression after electroporation was further demonstrated using an anthocyanin construct, which is specific for expression in plant cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01983234
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  • 5
    Electronic Resource
    Electronic Resource
    Crop yield and tree-leaf production in three planting patterns of temperate-zone alley cropping in Oregon, USA (1999)
    Springer
    Agroforestry systems 46 (1999), S. 273-288 
    Details
    ISSN: 1572-9680
    Keywords: A,nus rubra ; hedgerow intercropping ; Robina pseudoacacia ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The objective of this study was to determine crop and tree productivity in several alley cropping planting patterns. The four- year study was conducted in western Oregon, United States and involved irrigated sweet corn (Zea mays) intercropped between hedgerows of red alder (Alnus rubra) and black locust (Robina pseudoacacia). Three alley cropping planting patterns with variable plant populations and tree-crop proximity were tested with each tree species in a randomized block design. Space available to trees and crops determined yield of both plant components. High crop yield coincided with low pruning yield, and vice versa. Compared to monocropping, yield reductions in traditional alley cropping planting patterns with widely spaced, double tree rows ranged from 5% to 15%. A. rubra and R. pseudoacacia coppiced readily and produced 0.9 to 4.7 tons of dry matter pruning biomass per growing season, depending on planting pattern and year. A. rubra yield continually increased during the trial, while the ability of R. pseudoacacia to produce green manure after frequent coppicing appeared to weaken. After four years, soil organic matter was 4 to 7% higher in the topsoil of an alley cropping system compared to a monocropping system. However, continuous growing of sweet corn resulted in decreased soil organic matter levels in both cropping systems compared to original levels. Crop yield reductions and the need for additional management inputs constrain the implementation of alley cropping in temperate climates. Only if benefits other than minor soil fertility improvements are realized is alley cropping a feasible alternative in temperate climate regions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006204018212
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  • 6
    Electronic Resource
    Electronic Resource
    Early post-pollination events in hexaploid wheat × maize crosses (1990)
    Springer
    Sexual plant reproduction 3 (1990), S. 70-76 
    Details
    ISSN: 1432-2145
    Keywords: Wheat ; Maize ; Hybridization ; Fertilization ; Karyogamy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cytological events in the first 12 h after pollination were studied in crosses between the hexaploid wheat genotype Chinese Spring and the maize genotype Seneca 60. A pollen tube was first observed in the embryo sac 4 h after pollination, and maize sperm nuclei were first observed in the embryo sac after 5 h. On 29 occasions two, and on 1 occasion three, pollen tubes penetrated the embryo sac. Four categories of aberration limiting the frequency of fertilization were identified: (1) in 20% of florets no pollen tube reached the embryo sac; (2) in at least 1.9% the pollen tube severely damaged the wheat egg cell and polar nuclei; (3) in 33% the maize sperm nuclei were not released from the pollen tube; and (4) in 16% the sperm nuclei were released into the embryo sac but failed to move to either of the wheat gametes. In the remaining 29% sperm nuclei were more often found in the egg cell than at the polar nuclei. The results suggest that karyogamy occurs with very high efficiency when a sperm nucleus reaches the egg cell, but with only about 50% efficiency when a sperm nucleus reaches the polar nuclei.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00189954
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  • 7
    Electronic Resource
    Electronic Resource
    Effects of calcium, magnesium, potassium and boron on sperm cells isolated from pollen of Zea mays L. (1995)
    Springer
    Sexual plant reproduction 8 (1995), S. 113-122 
    Details
    ISSN: 1432-2145
    Keywords: Zea mays ; Calcium ; Cell integrity ; Cell viability ; Sperm cell
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Our previous studies showed that Brewbaker and Kwack salts, which have been widely used in pollen germination and sperm isolation, are not appropriate for the maintenance of isolated maize (Zea mays L.) sperm cells. In the present study, we have characterized the effects of each BKS component salt on the integrity of isolated sperm cells using hemacytometry. At 0.01 and 0.1 mM, there were no differences in cell number between control and any salt-treated cells except a 22% decrease with 0.1 mM MgSO4 at 48 h. At the 1 mM level, cell number decreased with time in the presence of Ca(NO3)2 and MgSO4, with loss of integrity of most cells at 48 h, while KNO3 and H3BO3 had little or no effect. Further characterization of calcium-induced reduction in cell integrity using flow cytometry showed that depletion of possible residual free calcium by addition of EGTA to the suspension medium improved cell longevity and viability. Exposure of isolated sperm cells to 1 mM calcium had no effect on cell integrity and viability in 5 h; however, only 12% of cells remained intact at 24 h. The reduction in cell integrity was hastened when cells were pretreated with the calcium ionophore A23187 prior to exposure to 1 mM calcium, with a 54% reduction in cell number at 1 h and complete cell lysis at 24 h. However, depletion of cytosolic free calcium by pretreatment of cells with the calcium ionophore followed by resuspension in the presence of EGTA resulted in rapid reduction of cell integrity as well. These results collectively suggest that maize sperm cells are sensitive to exogenous free calcium; however, a certain level of cytosolic free calcium is necessary for maintenance of integrity. Mechanisms of calcium-induced reduction in cell integrity are discussed along with possible roles of the sensitivity of sperm cells to calcium in fertilization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230898
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  • 8
    Electronic Resource
    Electronic Resource
    Differential expression of six glutamine synthetase genes in Zea mays (1993)
    Springer
    Plant molecular biology 23 (1993), S. 401-407 
    Details
    ISSN: 1573-5028
    Keywords: gene-specific probes ; glutamine synthetase ; transcript accumulation ; Zea mays
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The maize genome has been shown to contain six glutamine synthetase (GS) genes with at least four different expression patterns. Noncoding 3′ gene-specific probes were constructed from all six GS cDNA clones and used to examine transcript levels in selected organs by RNA gel blot hybridization experiments. The transcript of the single putative chloroplastic GS2 gene was found to accumulate primarily in green tissues, whereas the transcripts of the five putative GS1 genes were shown to accumulate preferentially in roots. The specific patterns of transcript accumulation were quite distinct for the five GS1 genes, with the exception of two closely related genes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00029015
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  • 9
    Electronic Resource
    Electronic Resource
    The effect of the crossability loci Kr1 and Kr2 on fertilization frequency in hexaploid wheat x maize crosses (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 403-409 
    Details
    ISSN: 1432-2242
    Keywords: Wheat ; Maize ; Crossability genes ; Chromosome elimination ; Haploids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Dominant alleles of the Kr1 and Kr2 genes reduce the crossability of hexaploid wheat with many alien species, including rye and Hordeum bulbosum, with Kr1 having the greater effect. However, a cytological study of wheat ovaries fixed 48 h after pollination showed that the wheat genotypes ‘Highbury’ (kr1, Kr2) and ‘Chinese Spring (Hope 5B)’ (kr1, kr2) were crossable with ‘Seneca 60’ maize, fertilization occurring in 14.4 and 30.7% of embryo sacs respectively. The latter figure was similar to the 29.7% fertilization found in ‘Chinese Spring’ (kr1, kr2). Most embryo sacs in which fertilization occurred contained an embryo but lacked an endosperm and where an endosperm was formed it was usually highly aberrant. All three wheat x maize combinations were karyotypically unstable and rapidly eliminated maize chromosomes to produce haploid wheat embryos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262508
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  • 10
    Electronic Resource
    Electronic Resource
    Production of normal, germinable and viable pollen from in vitro-cultured maize tassels (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 521-526 
    Details
    ISSN: 1432-2242
    Keywords: Zea mays ; Fertilization ; In vitro pollen ; In vitro culture ; Uniformity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Immature tassel meristems (1.0–1.5 cm long) of Zea mays L. inbred, Oh43, and single cross hybrid, Se60, cultured on a nutrient liquid medium underwent extensive development through to maturity and produced normal, mature, trinucleate pollen grains. The grains germinated on nutrient agar and on receptive silks and also produced viable kernels. No differences were observed between in vitro-produced pollen and in vivo pollen (pollen from greenhouse-grown plants) in characteristics such as pollen size, in vitro and in situ germination, and pollen tube growth in vitro. The kernels produced with in vitro pollen grew into mature plants (in vitro plants) which were similar to in vivo plants (plants produced with in vivo pollen), with no significant differences for all the morphological characteristics measured, and no phenotypic and cytological abnormalities. Gel electrophoresis of polypeptides revealed no major differences between in vitro and in vivo seedlings. This demonstration of fertilization and production of normal, uniform plants with pollen from cultured tassels has significant potential in basic and applied research studies.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00274273
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