Effect of photoinhibition on algal photosynthesis: a dynamic model

Recent evidence from algal physiology and molecular biology confirms that p hotoinhibition is directly related to D1 protein damage and recovery, and D 1 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 relativ e concentration of D1 protein in reaction centre II and the photoinhibition processes due to D1 protein degradation are incorporated into a model of p hotosynthesis, initiated by Dubinsky et al. (Plant Cell Physiol., 27, 1335- 1349. 1986) and developed by Sakshaug et al. (Limnol. Oceanogr., 34, 198-20 5, 1989). D1 protein damage is assumed to be both Light and D1 protein conc entration dependent, and to be proportional to the cross-section of PSII (s igma(PSII)). D1 protein recovery is only D1 protein concentration dependent . Two parameters, the damage constant (k(d)) and recovery rate (k(r)), are introduced to formulate the dynamics of D1 protein concentration. Setting m inimal turnover time tau(m) = 3 ms, maximal quantum yield phi(m) = 0.1 mol O-2 E-1, optical cross-section a* = 0.0075 m(2) (mg Chi a)(-1), sigma(PSII) = 2 nm(2), k(d) ranging from 0 to 10(-7) and k(r) = 0.55 h(-1), the dynami c effect of photoinhibition on photosynthesis in natural conditions is simu lated. Simulation results are consistent with observations. Some aspects of photosynthesis associated with photoinhibition, e.g. nutrient limitation a nd the interaction between photoinhibition and photoadaptation, are investi gated through this dynamic model.