【作者】 陈晓英；

【导师】 高辉远；

【作者基本信息】 山东农业大学 ， 植物学， 2003， 硕士

【摘要】 本文以适应于不同光强的玉米和大豆为材料，研究高温（42℃, 24h）处理对玉米和大豆光合作用、激发能分配和光破坏防御机制的影响，分析了高温处理前后大豆光呼吸在保护光合机构，耗散过剩激发能中所起的作用，探讨了适应于不同光强的玉米和大豆叶片对高温处理有不同响应的原因。主要结果如下：1． 高温处理后，适应于强光的玉米和大豆叶片饱和光合速率下降程度大于适应于弱光的叶片，光合速率的降低是由于非气孔因素造成的。2． 高温处理后，适应于强光的玉米和大豆叶片的PSII反应中心失活严重，捕获的激发能中用于光化学反应的大幅度减少；而适应于弱光的叶片的PSII反应中心失活较轻，捕获的激发能中用于光化学反应的略有减少。3． 高温处理后，适应于强光的玉米和大豆叶片的电子传递受到了显著抑制，QA向QB电子传递速率下降，还原态的QA- 大量积累，可能是由于QB的丢失或降解造成的，也可能与D1、D2蛋白的构象发生了变化有关；适应于强光的玉米和大豆叶片受体侧的电子传递的降低还与快PQ组分的减少有关。适应于弱光的玉米和大豆叶片受体侧的电子传递受到的影响较小。适应于不同光强的玉米和大豆叶片高温处理后电子传递受到的影响不同，与类囊体的跺叠程度及高温处理后膜结构受到的破坏程度有关。 4． 高温处理引起适应于不同光强的玉米和大豆叶片的热耗散均增加，其中有一部分是不依赖于叶黄素循环的能量耗散。高温处理后适应于弱光的玉米叶片依赖于叶黄素循环的热耗散增强，可能与高温处理增加了叶黄素的扩散有关。经高温处理后，适应于强光的大豆叶片的光呼吸绝对值明显降低，光呼吸与总光合速率的比值增加较小，光呼吸对φPSII，Fv’/Fm’，qP和NPQ基本上没有影响，说明高温处理后光呼吸在适应于强光的大豆的光破坏防御机制中可能并不起重要作用。而阴生大豆叶片的光呼吸在高温处理后绝对值增加，光呼吸与总光合速率的比值增加显著，光呼吸对激发能分配也产生了较大的影响，说明在高温处理后阴生大豆的<WP=7>5． 光呼吸在维持电子传递和耗散过剩光能中起比较重要的作用。6． 高温处理引起适应于不同光强的玉米和大豆叶片色素含量的变化，Chl a/b 比值和类胡萝卜素含量增加，适应于弱光的叶片Chl a/b 比值和类胡萝卜素含量增加显著。类胡萝卜素含量的增加在清除活性氧以保护膜结构中起重要作用。7． 高温处理对适应于强光的玉米和大豆的膜系统伤害较大，其电解质外渗和膜脂过氧化程度都比适应于弱光的叶片严重。8． 适应于强光的大豆叶片反应中心活性受高温影响较大，而玉米叶片较低。适应于弱光的大豆叶片反应中心活性受高温影响最小，可能与其高温处理后光呼吸和类胡萝卜素含量的增加有关。更多还原

【Abstract】 The effects of heat stress（42℃, 24h）on photosynthesis, energy distribution and photodamage defence mechanism of maize and soybean leaves acclimated to different light regimes were studied. The influences of photorespiration on protection of photosynthetic organism and the distribution of excess excitation energy in soybean leaves before and after heat stress were analyzed. The possible reasons of the different responses to heat stress in both maize and soybean leaves were discussed. The main results are as follows: 1. The decreases of photosynthesis in sun-acclimated maize and soybean leaves after heat stress were greater than that in the shaded ones. The decrease was caused by non-stomatal restriction. 2. After heat stress, the PSII reaction centers of sun-acclimated maize and soybean leaves were severely inactivated, and the use of captured excitation energy via photochemical reaction was significantly reduced. In contrast, the inactivation of the PSII reaction center, the reduction of energy distribution to photochemistry in shade-acclimated maize and soybean leaves were less affected. 3. After heat stress, the electron transport was badly inhibited in sun-acclimated maize and soybean leaves. The electron transport from QA to QB was reduced, resulting in the largely accumulated QA－. The accumulation of QA－ might be caused by the lost or the disintegration of the QB protein, it might also correlate to the changes of the conformation of the D1/D2 protein. The loss of the fast PQ pool also contributed to the decrease of the receptor side electron transport in the sun-acclimated maize and soybean leaves. In contrast, the receptor side electron transport of the shade-acclimated maize and soybean leaves was slightly affected. The different responses of the electron transport in maize and soybean leaves acclimated to different light regimes might be related to the degree of thylakoid stacking and the destroy of the membrane caused by heat stress.Heat stress induced the increase of the thermal energy dissipation,<WP=9>4. including the part of the xanthophyll-cycle-independent ones, in both sun and shade plants. The xanthophyll-cycle-dependent energy dissipation was increased in shade-acclimated maize leaves after heat stress, probably due to the increase of the diffusion of the xanthophylls.5. After heat stress, the absolute value of photorespiration was markedly decreased while the ratio of the photorespiration to mass photosynthetic rate was slightly increased in sun-acclimated soybean leaves. It’s photorespiration had little effect on theφPSII, Fv’/Fm’, qP and NPQ. All this indicated that photorespiration might play a minor role in photoprotection in sun plants after heat stress, wheareas in the shade-acclimated soybean leaves, photorespiration might perform an important function in the maintain of the electron transport and the distribution of the excess light energy in the shade-acclimated soybean leaves after heat stress.6. The content of pigments in both sun- and shade-acclimated maize and soybean leaves were changed after heat stress. The Chl a/b ratio and the content of the carotenoids were increased markedly in the shaded leaves. The increase of the content of the carotenoids played an important role in the detoxifying of the active oxygen and the protection of the membrane. 7. The membrane of the sun-acclimated maize and soybean leaves were notably damaged, as the leakage of the electrolyte and the overoxidation of membrane lipids were more severe than that in the shade ones.8. The activities of PSII reaction center in sun-acclimated soybean leaves were mostly affected compared to the other plants, while the shade-acclimated soybean leaves were the least affected, due probably to the increase of the photorespiration and the content of carotenoids after heat stress.更多还原