光氧化条件下碳代谢中间产物与光合电子传递对PSⅡ光化学活性的调节作用

The Modulation of PSII Photochemical Activity by Carbon Metabolic Intermediates and Photosynthetic Electron Transport under Photooxidation Conditions

摘要:

在MV和强光的光氧化条件下研究外加光合碳代谢中间产物、光呼吸C2酸和光合电子传递抑制剂等对菠菜叶绿体PSⅡ光化学活性的调节作用。结果表明，光氧化条件下外加“RuBP再生系统”和乙醇酸钠可提高qP和Φ_PSⅡ，而R5P、DHAP和HCO₃^-可提高qN，显示其对光氧化下叶绿体PSⅡ活性有一定程度的保护作用。其他外加化合物3-PGA、3-GAP、HPMS、DCMU、DBMIB、Ant A、短杆菌肽D等则对以叶绿素荧光参数表示的光化学活性和氧电极测定的全链电子传递速率表现抑制效应。据此认为在叶绿体水平上阻断或改变光合电子流的流向，更改光合碳还原和光呼吸代谢物浓度，皆可直接或间接影响光氧化下PSⅡ的光化学活性，其作用因不同化合物而异。

Abstract:

PSII photochemical activity and electron transport rate of whole chain (PSII+PSI) in spinach chloroplasts were measured under photooxidation (MV plus strong light) with or without addition of various exogenousphotosynthetic carbon metabolic intermediates, Na-glycolate and inhibitors of photosynthetic electron transport. The results indicated that under photooxidation condition, the addition of "RuBP regeneration system" and sodium glycolate increased qP and Φ_PSⅡ, while R5P, DHAP and HCO₃^- increased qN,compared to nonphoto-oxidative contro1．Other chemicals，3-PGA，3-GAP，HPMS，DCMU，DBMm， Ant A and gramicidin D all showed an inhibitory efect on PSII photochemical activity (expressed by chlorophyll fluorescence parameters)and electron transport rate of PSII+PSI(determined by oxygen electrode)． It is proposed that carbon metabolic intermediate could act as a physiological regulator to modulate PSII photochemical activity. Alteration or blocking the flux / direction of photosynthetic electron transport，and changing the concentration of metabolites in Calvin cycle and photorespiratoy C₂ acid cycle would cause a direct or indirect efect on PSII activity under photooxidation condition．The effect varied with diferent chemicals．