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A mathematical model for photoinhibition of leaf photosynthesis was developed by formalising the assumptions that (1) the rate of photoinhibition is proportional to irradiance; and (2) the rate of recovery, derived from the formulae for a pseudo first-order process, is proportional to the extent of inhibition. The photoinhibition model to calculate initial photo yield is integrated into a photosynthesis-stomatal conductance (g
s) model that combines net photosynthetic rate (P
N), transpiration rate (E), and g
s, and also the leaf energy balance. The model was run to simulate the diurnal courses of P
N, E, g
s, photochemical efficiency, i.e., ratio of intercellular CO2 concentration and CO2 concentration over leaf surface (C
i/C
s), and leaf temperature (T
1) under different irradiances, air temperature, and humidity separately with fixed time courses of others. When midday depression occurred under high temperature, g
s decreased the most and E the least. The duration of midday depression of g
s was the longest and that in E the shortest. E increased with increasing vapour pressure deficit (VPD) initially, but when VPD exceeded a certain value, it decreased with increasing VPD; this was caused by a rapid decrease in g
s. When air temperature exceeded a certain value, an increase in solar irradiance raised T
1 and the degree of midday depression. High solar radiation caused large decrease in initial photon efficiency (). P
N, E, and g
s showed reasonable decreases under conditions causing photoinhibition compared with non-photoinhibition condition under high irradiance. The T
1 under photoinhibition was higher than that under non-photoinhibition conditions, which was evident under high solar irradiance around noon. The decrease in C
i/C
s at midday implies that stomatal closure is a factor causing midday depression of photosynthesis. 相似文献
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