C3和C4植物叶片对光氧化响应的日变化

DIURNAL CHANGES OF PHOTOOXIDATION RESPONSE IN LEAVES OF C3 AND C4 PLANTS

摘要:

田间生长的C₃植物花生和C₄植物玉米分别于晴天上午9：00、中午12：00、下午15：00取样。中午12：00花生叶片的Fv／Fm较早上9：见下降16％，出现了光抑制现象，玉米叶片的Fv／Fm则未下降。不同时间取样的花生和玉米叶片经甲基紫精（MV）+强光的人为光氧化处理，叶绿素和类胡萝卜素出现不同程度的氧化降解，中午12：00降解幅度最大，15时降幅最小。植物叶片的抗氧化能力与其SOD活性相关，而与PEPCase的活性没有明显的相关性。光氧化处理后，花生和玉米的叶绿素荧光参数FV／Fm、q_p、pSII都下降，花生在12：00的降幅最小，玉米的降幅最大。光氧化引起花生的qN和热耗散系数（KD）上升，玉米则都下降．结果显示C₃植物花生和C₄植物玉米对光氧化的响应可能存在不同的机制。

Abstract:

Diurnal changes of SOD, POD and PEPCase activities, pigment contents and chlorophyll fluorescence parameters were compared between C₃ plant peanut (Arachis hypogaea) and C₄ plant maize (Zea mays) under natural condition and photooxidation condition. Plant leaves were collected at g:00(a.m.), 12:00(noon) and 15t00(p.m.) in the field during a day, respectively, and then treated by 500 umol/L methyl viologen (MV) under 1500 umol m^-2s^-1 light intensity for 30 min. In the midday (12: 00), Fv/Fm in untreated peanut leaves decreased by 16% indicating that the photoinhibition occured, while that in untreated maize leaves showed no change. After MV-photooxidation treatment, the maximal decrease in chlorophyll and carotenoid were found in both peanut and maize leaves at 12:00. The antioxidative ability was related to SOD activity but seemed not to be related to PEPCase activity. Under MV-photooxidation, Fv/Fm, q_p and PSII were found to have a maximal decrease in maize leaves and a minimal decrease in-peanut leaves at 12: 00. MV-induced q_N and KD (coefficient of heat dissipation) were increased in peanut leaves but decreased in maize leaves during a day. It is proposed that a different mechanism in response to photooxidation may exist between C₃ plant and C₄plant.