Effect of photoinhibition on algal photosynthesis: a dynamic model

Abstract

Recent evidence from algal physiology and molecular biology confirms that photoinhibi- tion is directly related to D1 protein damage and recovery, and D1 protein damage leads to a decrease in electron transfer or an increase in turnover time of the electron transfer chain. In this study, the turnover time of the electron transfer chain is defined as a function of the relative concentration of D1 protein in reaction centre II and the photoinhibition processes due to D1 protein degradation are incorporated into a model of photosynthesis, initiated by Dubinsky et al. (Plant Cell Physiol., 27, 1335-1349, 1986) and developed by Sakshaug et al. (Limnol. Oceanogr., 34, 198-205, 1989). D1 protein damage is assumed to be both light and D1 protein concentration dependent, and to be proportional to the cross-section of PSII (σ PSII). D1 protein recovery is only D1 protein concentration dependent. Two parameters, the damage constant (kd) and recovery rate (kr), are introduced to formulate the dynamics of D1 protein concentration. Setting minimal turnover time τm � 3 ms, maximal quantum yield φm � 0.1 mol O2 E-1, optical cross-section a* � 0.0075 m2 (mg Chl a)-1, σ PSII � 2n m 2, kd ranging from 0 to 10-7 and kr � 0.55 h-1, the dynamic effect of photoinhibition on photo- synthesis in natural conditions is simulated. Simulation results are consistent with observations. Some aspects of photosynthesis associated with photoinhibition, e.g. nutrient limitation and the interaction between photoinhibition and photoadaptation, are investigated through this dynamic model.