光抑制条件下不同水稻品种叶片的PSⅡ光化学效率和CO_2交换特性的差异

Varietal Differences in Photochemical Efficiency of PS Ⅱ and Features of CO_2 Exchange in Rice Leaves Under Photoinhibitory Conditions

比较了光抑制条件下两个水稻品种叶片的PSⅡ电子传递活性、D1蛋白量、叶绿素荧光Fv／Fm、净光合（PN）和光呼吸（PR）速率、碳酸酐酶（CA）、PEPC和RuBP羧化／加氧酶活性的变化，并对RuBP羧化酶进行了动力学分析。经光抑制处理后，耐光抑制品种02428较对光抑制敏感品种3037中D1蛋白净降解少、PSⅡ活性和PSⅡ原初光化学效率高，光抑制较轻；RuBP羧化／加氧酶活性和RuBP羧化酶的Km（CO2）和Vmax（CO2）值没有变化，且在品种间无差异。CA和PEPC活性出现诱导增高，尤以品种02428中活性诱导的幅度更高。CO2交换特点发生了显著变化，在PN降低的同时，Pa／PN比值明显增加，品种3037的PR／PN比值比02428的更大。在水稻耐光抑制特性上，D1蛋白、CA和PEPC可能分别对PSⅡ光化学效率和CO2交换起着重要的调节作用。

The changes of PS Ⅱ electron transport activity, D1 protein content, chlorophyll fluorescence parameter Fv/Fm, net photosynthetic rates (PN ), photorespiratory rates (PR) , activities of carbonic anhydrase(CA) and PEPC and RuBPCase/Oase, as well as the kinetic property of RuBPCase were measured in rice leavesunder photoinhibitory conditions. Photoinhibition- tolerant variety 02428 showed a less net degradation of D1 protein (or maintaining higher level of D1 protein ), higher electron transport activity and primary photochemical efficiency of PS Ⅱ, and less photoinhibition after illumination under a photon flux density (PFD) of 1000 μmol photons/m2s in 21% O2 and CO2-free gas for 3 hours, as compared with photoinbibition -sensitive variety 3 0 3 7.However, no difference of RuBPCase/Oase activities and values of K. (CO2) and Vmax.(CO2) between two varietieswere found either before or after photoinhibition. The increasing activities of CA and PEPC were induced underphotoinhibitory conditions, and which were higher in variety 02428 than in variety 3037. Furthermore, the ratioof PR to PN(PR/PN) increased while the PN decreased in both varieties, but variety 3037 showed higher PR/PN valuethan variety 02428. According to the results mentioned above, it is proposed that D1 protein, CA and PEPCmight play an important role respectively in regulating photochemical efficiency of PS Ⅱ and CO2 exchange for photoinhibition tolerance.