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Twenty-six provenances (2 340 plants) of cork oak (Quercus suber spp.) originating from Portugal, Spain, Italy, Morocco, Algeria, and Tunisia were tested for genetic variation among and within provenances by growth traits. Seven morphometrical characters were measured in 90 plants from each provenance. Analysis of variance showed highly significant differences for all characters. The phenotypic coefficient of differentiation reached 0.24 for the form and 0.22 for height, thus revealing a strong structuring between the provenances. Comparative study of growth among the provenances revealed more vigorous growth and better survival rate for those from Morocco, Spain, and Portugal, which may constitute better materials for afforestation. Furthermore, this variability appeared to be geographically structured and would be mainly genetically controlled, as cork oak provenances were cultivated under the same environmental conditions. Our results should be helpful for guide forest managers in afforestation.  相似文献   
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Genetic Resources and Crop Evolution - The genus Brachypodium is generally considered taxonomically difficult because of the high levels of phenotypic variation and frequent...  相似文献   
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The possibility to use membrane‐lipid measurements to screen barley genotypes for salt resistance was studied. The results showed that wild barley (Hordeum maritimum) displayed a typical halophytic response as compared to cultivated barley (Hordeum vulgare L. cv. Manel). Growth, tissue hydration, and photosynthetic activity were less affected by salinity in H. maritimum than in H. vulgare. The induced effects of long‐term NaCl treatment were reflected in root membrane lipids that remained relatively unchanged in wild barley, whilst they were significantly diminished with increasing salinity in H. vulgare. The levels of membrane‐lipid peroxidation and electrolyte leakage were changed only at high salt concentrations in H. maritimum whereas those of H. vulgare were considerably increased by lower salinity levels as a result of oxidative damage. These findings indicate that maintained membrane integrity (in H. Maritimum) may be considered a possible trait for salt resistance. However, membrane fluidity in H. vulgare was more increased than in H. maritimum. Thus, the unsaturated–to–saturated fatty acid ratio (UFAs : SFAs) and the double‐bond index (DBI), significantly increased in response to salt stress in cultivated barley while it did not change in H. maritimum. The changes in lipid unsaturation were predominantly due to increases in linolenic (C18:3), linoleic (C18:2), and oleic (C18:1) acids and decreases in stearic acid (C18:0). These results suggest that, in spite of being important for maintenance of membrane fluidity, the ability to increase unsaturation is not a determinant factor for salt resistance in barley species.  相似文献   
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Growth, activity of antioxidant enzymes viz. glutathione reductase (GR), superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX), and some metabolic processes related to ammonium metabolism were investigated in a salt‐tolerant Spatina alterniflora. In comparison to 0 mM–NaCl treatment, growth of S. alterniflora plant increased significantly at 200 mM NaCl, but was highly inhibited at 500 mM NaCl. Ammonium concentration in the leaves and roots increased 2.1–3.4 times when plants were treated with 500 mM NaCl. Under 200 mM NaCl, antioxidant‐enzyme activities increased, however, at 500 mM the antioxidant system was unable to compensate reactive oxygen species induced by NaCl. At this high level of salinity, ammonium production through nitrate reductase (NR) was inhibited, but no significant changes in the activities of glutamine synthetase (GS) or glutamate dehydrogenase (GDH) were found. We conclude that the accumulation of ammonium under high salt stress was not due to inhibition of the assimilatory activities of GS or GDH. Ammonia accumulation under high salinity may result from amino acid and protein catabolism activated by reactive oxygen species (ROS) and/or a lack of carbon skeletons to incorporate ammonium into organic molecules due to a decrease in photosynthetic activity in salt‐stressed plants.  相似文献   
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