Abstract: To elucidate the protective mechanisms against photodamage in photosynthetic apparatus of rice, the difference in traits related to xanthophyll cycle, chlorophyll fluorescence and photosynthetic CO₂ exchange among indica japonica hybrids and their parents under midday strong light were studied. Obviously diurnal variation of apparent quantum yield (AQY), D1 protein content, ratio of photorespiration/photosynthesis (P_r/P_n), PS Ⅱ photochemical efficiency (F_v/F_m),non photochemical quenching (q_N) and xanthophyll cycle[content of violaxanthin(V), antheraxanthin(A), and zeaxanthin(Z)]in leaves of different genotype rice were observed. Japonica rice kept higher D1 protein content, F_v/F_m and AQY, but lower level of (A+Z)/(A+Z+V), P_r/P_n and q_N, as compared with indica rice. However, the physiological parameters mentioned above in reciprocal cross F₁ hybrids were between those of their parents, but closed to their maternal lines. The lower AQY and F_v/F_m and higher (A+Z)/(A+Z+V) and P_r/P_n in indica/japonica F₁ hybrids than in japonica/indica F₁ hybrids were depended on different source of their plastid genes. Data processing showed that markedly positive correlation between D1 protein content and F_v/F_m or AQY and negative correlation between D1 protein content and (A+Z)/(A+Z+V),P_r/P_n or q_N were presented. Besides, a positive correlation between (A+Z)/(A+Z+V) and q_N was also observed. Furthermore, there was less zeaxanthin content and , as a result, more net loss of D1 protein in the leaves treated with dithiothretol (DTT) than those in control leaves under midday strong light. According to these results, the levels and stabilities of D1 protein encoded by plastid gene from maternal line were proposed as the main physiological basis of the difference in characteristics related to xanthophyll cycle, chlorophyll fluorescence and photosynthetic CO 2 exchange among different genotypes of rice, and the xanthophyll cycle in leaves played an important role in protecting photosynthetic apparatus against photodamage.

Key words: xanthophyll cycle, chlorophyll fluorescence, photosynthesis, photoinhibition, rice

摘要： 以籼亚种3037、Palghar (对光抑制敏感)和粳亚种02428、029(耐光抑制)及其籼粳亚种间杂种F1为材料进行试验。 水稻叶片中叶黄素循环(叶黄素组分紫黄质、环氧玉米黄质、玉米黄质的含量V、A、Z)、Pr/Pn、非光化学猝灭(qN)、表观光合量子效率(AQY)、PSⅡ光化学效率(Fv/Fm)和D1蛋白量有明显的日变化，且在不同基因型水稻间有显著差异。在午间强光下，与籼亚种相比，粳亚种有较高的AQY、Fv/Fm和D1蛋白量，较低的(A+Z)/（A+Z+V）、Pr/Pn和qN值，籼粳正反交F1杂种的上述生理指标介于双亲值之间，且偏向其母本。相关分析表明，D1蛋白量与Fv/Fm或AQY之间有极显著的正相关关系，与 (A+Z) /（[WTBX]A+Z+V[WTBZ]）或Pr/Pn或qN之间有显著的负相关关系， (A+Z) /（A+Z+V）与qN之间有极显著的正相关关系。叶黄素循环抑制剂DTT使午间强光下玉米黄质的含量明显降低，结果导致D1蛋白更多地降解。上述证据证明，质基因编码的D1蛋白水平、稳定性是水稻不同基因型间叶黄素循环和CO2交换特性差异的生理基础，叶黄素循环在保护光合机构避免强光破坏中起重要作用。

关键词: 叶黄素循环, 叶绿素荧光, 光合作用, 光抑制