The paper studied germination characteristics, dehydration sensitivities, and antioxidative enzyme activities of seeds in three varieties of Camellia sinensis L.[C. sinensis var. sinensis cv. Fuding-dabaicha (Fd), C. sinensis var. assamica cv. Menghai-dayecha (Md), and C. sinensis var. assamica cv. Yunkang 10 (Y10)] during desiccation. The optimum germination temperature was 25°C for Fd, 30°C for Md, and 20°C for Y10. Md, Y10, and Fd seeds were all sensitive to dehydration. GPs of three cultivars decreased dramatically after dehydration for 144 h, reaching values of 48, 37, and 57 % for Md, Y10, and Fd when moisture content declined to 17.5, 17.4, and 14.4 %, respectively. The antioxidative enzymes in Md, Y10, and Fd seeds were not as effective as orthodox seeds, none of them can scavenge ROS timely. Thus, lipid peroxidation accelerated. There were differences between seeds of the three cultivars: Fd seeds were smaller in shape than the other two; Fd seeds showed lower sensitivity to dehydration than the other two; and H 2 O 2 contents in Fd seeds were obviously lower than in Md and Y10 seeds, indicating that antioxidative enzymes in Fd seeds were more effective than the other two.
Different plants and plant organs have various strategies to cope with drought stress.Kalanchoe tubifloraplants have a strong ability to prevent water loss and to scavenge reactive oxygen species. The epiphyllous bud of the plant serves as a reproduction unit and is able to generate plantlets even under conditions of extreme drought. The aim of this project was to study the antioxidant-stress response and osmoregulation ofK. tubifloraepiphyllous buds to dehydration and to compare the drought-tolerance mechanisms of the plant body and the epiphyllous buds. With the progression of bud dehydration, relative water content, seedling survival rate and dry weight per seedling decreased, and electrolyte leakage, hydrogen peroxide and malondialdehyde content and superoxide anion production rate increased. The activities of the antioxidant enzymes superoxide dismutase, catalase, ascorbate peroxidase, dehydroascorbate reductase and glutathione reductase decreased under dehydration. The content of proline, soluble sugars and soluble protein increased in dehydrated buds proportionally with the extent of water loss. These data indicate that the drought-tolerance mechanism of theK. tubiflorabud was different from that of its mother plant. The buds invest more energy to prevent water loss during drought stress, and their antioxidant defense weakens.
The subcellular localization of calcium in Alpinia mutica Roxb. during style movement was studied in two morphs. In the styles, Ca-antimonate precipitates (ppts) were principally located in apoplasts, with some minimal accumulation in the nucleus. At different movement, stages of movement, the ppts in the abaxial and adaxial sides changed, and no lateral gradient of ppts in the apoplast was established. The increase or decrease of ppts in the apoplast was not accompanied with equivalent changes in the cytoplasm. These results indicate that calcium could not affect the curvature by inhibiting cell elongation but may play a role in style movement by acting as a secondary messenger. EGTA-treatment affected style movement, providing further evidence supporting a role for calcium as a secondary messenger.
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