Four winter wheat (Triticum aestivum L.) varieties ('JD 8', 'Jing 411','Centurk' and 'Tam 202') were used to study the effect of heat stress on photosynthetic characteristics of flag le...Four winter wheat (Triticum aestivum L.) varieties ('JD 8', 'Jing 411','Centurk' and 'Tam 202') were used to study the effect of heat stress on photosynthetic characteristics of flag leaf blade, nag leaf sheath, peduncle, glume, lemma and awn during grain-filling stage. The results showed that heat acclimation during grain-filling stage increased thermotolerance of wheat with significant differences among different green organs. During heat stress, the decreases of the efficiency of primary light energy conversion (F-v/F-m) of PS II and pigment (chlorophyll and carotenoid) content were much slower in peduncle, flag leaf sheath and glume than in nag leaf blade, lemma and ann; and the percentage of decrease in net photosynthetic rate (P-n) of ear was lower than that of the nag leaf blade. The measured photosynthetic parameters (F-v/F-m, P-n and pigment content) of 'JD 8', a relatively heat tolerant variety, declined more slowly than those of the other three varieties during the whole heat stress period.展开更多
Levels of T1 （Thallium） in soil from 0 （control） to 50 μg/L through 0.2, 0.5, 1 and 2.5μg/L were directly and positively correlated to levels of T1 in plant tissue, the accumulation being maximum in roots, inter...Levels of T1 （Thallium） in soil from 0 （control） to 50 μg/L through 0.2, 0.5, 1 and 2.5μg/L were directly and positively correlated to levels of T1 in plant tissue, the accumulation being maximum in roots, intermediate in leaves and minimum in stems. Thallium, especially at higher concentrations, adversely affected photosynthesis （as judged based on chlorophyll fluorescence parameters）, suggesting inhibition of photo-activation of PSII （Photosystems II）, and also decreased the rate of photosynthesis, the rate of transpiration and stomatal conductivity drastically. Exposure to TI also increased the activity of CAT （Catalase） （except at 1 μg/L） and POD （Peroxidase） （except at 0.2 μg/L）, suggesting that the antioxidant systems in Coix lacryma-jobi were the main contributors of CAT and SOD （Superoxide Dismutase） and that the tolerance of C. lacryma-jobi to T1 is mainly due to this induced antioxidant machinery.展开更多
文摘Four winter wheat (Triticum aestivum L.) varieties ('JD 8', 'Jing 411','Centurk' and 'Tam 202') were used to study the effect of heat stress on photosynthetic characteristics of flag leaf blade, nag leaf sheath, peduncle, glume, lemma and awn during grain-filling stage. The results showed that heat acclimation during grain-filling stage increased thermotolerance of wheat with significant differences among different green organs. During heat stress, the decreases of the efficiency of primary light energy conversion (F-v/F-m) of PS II and pigment (chlorophyll and carotenoid) content were much slower in peduncle, flag leaf sheath and glume than in nag leaf blade, lemma and ann; and the percentage of decrease in net photosynthetic rate (P-n) of ear was lower than that of the nag leaf blade. The measured photosynthetic parameters (F-v/F-m, P-n and pigment content) of 'JD 8', a relatively heat tolerant variety, declined more slowly than those of the other three varieties during the whole heat stress period.
文摘Levels of T1 （Thallium） in soil from 0 （control） to 50 μg/L through 0.2, 0.5, 1 and 2.5μg/L were directly and positively correlated to levels of T1 in plant tissue, the accumulation being maximum in roots, intermediate in leaves and minimum in stems. Thallium, especially at higher concentrations, adversely affected photosynthesis （as judged based on chlorophyll fluorescence parameters）, suggesting inhibition of photo-activation of PSII （Photosystems II）, and also decreased the rate of photosynthesis, the rate of transpiration and stomatal conductivity drastically. Exposure to TI also increased the activity of CAT （Catalase） （except at 1 μg/L） and POD （Peroxidase） （except at 0.2 μg/L）, suggesting that the antioxidant systems in Coix lacryma-jobi were the main contributors of CAT and SOD （Superoxide Dismutase） and that the tolerance of C. lacryma-jobi to T1 is mainly due to this induced antioxidant machinery.
