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991.
Factor analysis of the data from experiment one with fertilization of ‘Spartan’ apples using various levels of nitrogen, phosphorus, and potassium and their interactions showed significances between ethylene and potassium, soluble solids and potassium, acidity and phosphorus, ethylene and phosphorus, and between ethylene and nitrogen. Factor analysis of data from experiment two with twenty apple cultivars showed that maturation time and ethylene were positively associated, whereas ethylene was inversely related to acidity that is reduced during the apple fruit maturation, and soluble solids are produced during apple fruit maturation. The effects of potassium on ethylene could be through promotion of enzyme activation, promotion of protein synthesis and increased solute transport in the xylem and phloem. Production of ethylene through soluble solids could be due to increased synthesis of the amino acid cysteine that is precursor of ethylene that may be extended to synthesis of other amino acids. The decreasing concentration of malic acid during fruit maturation may be due to increasing rates of several enzymes involved in the citric acid and glyoxylate cycles that are delivering precursors to synthesis of amino acids and porphyrins. The significant relationships between soluble solids and potassium and between acidity and phosphorus may increase the synthesis of nucleic acids and improve energy supply through adenosine phosphates. The significance between ethylene and nitrogen may also increase synthesis of amino acids, proteins and enzymes. On this basis it may be concluded that the three major minerals nitrogen, phosphorus and potassium are very important for apple fruit maturation because they may be involved in several biochemical processes. 相似文献
992.
993.
Marcos V. B. M. Siqueira Maria L. Bonatelli Torsten Günther Inka Gawenda Karl J. Schmid Vitor A. C. Pavinato Elizabeth A. Veasey 《Genetic Resources and Crop Evolution》2014,61(3):611-624
Substantial progress was made in the last decade in understanding the diversity in Dioscorea species. However, most of the studies so far concentrated in the ‘yam belt in Africa’. We present a genetic diversity and structure analysis among commercial and local varieties of water yam (Dioscorea alata L.) in Brazil using microsatellite and morphological markers. Twelve microsatellite primers were used to generate DNA profiles of 72 local varieties and 17 commercial accessions of water yam collected in four different regions in Brazil. Also, four morphological traits were evaluated on individual plants under field conditions. The morphological characterization showed considerable diversity. High polymorphism was found with 100 % polymorphism observed for 11 primers and a discriminating power value of 0.92, on average. We did not observe a strong population structure among sampling regions, while most of the genetic diversity was concentrated within regions (95.9 %). Analysis of the relationship between accessions did not clearly separate the local and commercial genotypes. However, the molecular analyses of D. alata showed high intraspecific diversity in local accessions from different regions in Brazil, with the highest Shannon index value (H′ = 0.41) for the Southeast region. These results confirmed an admixture of accessions in all sampling regions, consistent with the lack of a significant correlation between geographic and genetic distances, suggesting that farmers exchanged water yam materials extensively. The genetic diversity can be explained by the result of a continuous exchange of accessions by farmers throughout Brazil. 相似文献
994.
995.
Jörg Prietzel Karl Eugen Rehfuess Ulrich Stetter Hans Pretzsch 《European Journal of Forest Research》2008,127(1):43-61
Long-term (40 years) effects of two soil amelioration techniques [NPKMgCa fertilization + liming; combination of PKMgCa fertilization,
liming, tillage, and introduction of lupine (Lupinus polyphyllus L.)] on chemical topsoil properties, stand nutrition, and stand growth at two sites in Germany (Pfaffenwinkel, Pustert) with
mature Scots pine (Pinus sylvestris L.) forest were investigated. Both sites are characterized by base-poor parent material, historic N and P depletion by intense
litter-raking, and recent high atmospheric N input. Such sites contribute significantly to the forested area in Central Europe.
Amelioration resulted in a long-term increase of pH, base saturation, and exchangeable Ca and Mg stocks in the topsoil. Moreover,
significant losses of the forest floor in organic carbon (OC) and nitrogen stocks, and a decrease of the C/N ratio in the
topsoil were noticed. The concentrations and stocks of OC and N in the mineral topsoil increased; however, the increases compensated
only the N, but not the OC losses of the forest floor. During the recent 40 years, the N nutrition of the stands at the control
plots improved considerably, whereas the foliar P, K, and Ca concentrations decreased. The 100-fascicle weights and foliar
concentrations of N, P, Mg, and Ca were increased after both amelioration procedures throughout the entire 40-year period
of investigation. For both stands, considerable growth acceleration during the recent 40 years was noticed on the control
plots; the amelioration resulted in an additional significant long-term growth enhancement, with the NPKMgCa fertilization
liming + being more effective than the combination of PKMgCa fertilization, liming, tillage, and introduction of lupine. The
comprehensive evaluation of soil, foliage, and growth data revealed a key relevance of the N and P nutrition of the stands
for their growth, and a change from initial N limitation to a limitation of other growth factors (P, Mg, Ca, and water). 相似文献
996.
The changes of Eh and pH in soil suspension (Ah-horizon of a Mollic Gleysol) and Mn2+ or Fe2+ concentrations in the equilibrium soil solution at different levels of glucose (0%, 0.5% and 1%) and MnO2 (0%, 0.025%, 0.05% and 0.1%) or Fe2O3 (0%, 0.025%, 0.05% and 0.1%) were examined. It was found that the degree of Mn- and Fe-reduction in soil depends mainly on the presence and the amount of an easily decomposable carbon source and to a minor degree on the content of native or added forms of MnOO2 or Fe2O3 in the soil. Theoretical relationships between the water soluble manganese and iron and the Eh and pH values have been verified, when the observed initial drop of Eh was eliminated. It was found that the water soluble manganese content was described best by the Mn2O3/Mn2+ redox system, and that of iron by the Fe3 (OH)3/Fe2+ system. 相似文献
997.
998.
Salinity is a major constraint to irrigated rice production, particularly in semi-arid and arid climates. Irrigated rice is
a well suited crop to controlling and even decreasing soil salinity, but rice is a salt-susceptible crop and yield losses
due to salinity can be substantial. The objective of this study was to develop a highly predictive screening tool for the
vegetative growth stage of rice to estimate salinity-induced yield losses. Twenty-one rice genotypes were grown over seven
seasons in a field trials in Ndiaye, Senegal, between 1991 and 1995 and were subjected to irrigation with moderately saline
water (3.5 mS cm-1, electrical conductivity) or irrigation with fresh water. Potassium/sodium ratios of the youngest three leaves (K/NaLeaves) were determined by flame photometry at the late vegetative stage. Grain yield was determined at maturity. All cultivars
showed strong log-linear correlations between K/NaLeaves and grain yield, but intercept and slope of those correlations differed between seasons for a given genotype and between
genotypes. The K/NaLeaves under salinity was related to grain yield under salinity relative to freshwater controls. There was a highly significant
correlation (p < 0.001) between K/NaLeaves and salinity-induced grain yield reduction: the most susceptible cultivars had lowest K/NaLeaves and the strongest yield reductions. Although there were major differences in the effects of salinity on crops in both the
hot dry season (HDS) and the wet season, the correlation was equally significant across cropping seasons. The earliest possible
time to establish the relationship between K/NaLeaves under salinity and grain yield reduction due to salinity was investigated in an additional trial in the HDS 1998. About 60
days after sowing, salinity-induced yield loss could be predicted through K/NaLeaves with a high degree of confidence (p < 0.01). A screening system for salinity resistance of rice, particularly in arid and semi-arid climates, is proposed based
on the correlation between K/NaLeaves under salinity and salinity-induced yield losses.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
999.
1000.