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

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．