A review on light response model of photosynthesis under different environmental conditions

Light response curve of photosynthesis (A_n-I curve) is a useful modeling tool to investigate how photosynthesis reacts with different abiotic factors, which would help quantify the response of photosynthetic rate to photosynthetically active radiation. Based on the mathematical characteristics of photosynthesis A_n-I models, we reviewed the advantages of using these model in practice and the potential caveats. We proposed the development of new mechanistic photosynthesis A_n-I models based on the primary light response and discussed its advantages in the field of plant ecology and physiology. Photosynthesis has three main steps, including the primary reaction, the assimilatory power forms, and the carbon assimilation. Changes in each step could directly affect the photochemical efficiency and carbon assimilation in photosynthesis. The primary reaction consists of a series of physical processes that are related to light energy absorption and utilization, including the absorption of light energy, the change of quantum state, and the transfer and de-excitation of exciton resonance of light-trapping pigment molecules. How-ever, the empirical photosynthesis A_n-I models can not explain some scenarios. For example, the non-photochemical quenching in plants increases with increasing light intensity in a non-linear manner. Further, the life-time of singlet chlorophyll molecules can be extended when plant light-harvesting pigment molecules absorb excessive light energy but would not be immediately used for the photochemical reaction. Meanwhile, the parameters obtained by fitting the mechanistic A_n-I curve model can not only reflect the primary photochemical reaction characteristics of plants, but also describe the physical characteristics of plant light harvesting pigment molecules, such as the number of light harvesting pigment molecules in the excited state (N_k) and effective light energy absorption cross-section (σ_ik'). This can be used to further investigate the physical characteristics of light harvesting pigment molecules, including the light-response of N_k and σ_ik' and the average life time of light harvesting pigment molecules in the lowest exciting state (τ_min). In addition, it would be necessary to determine how to incorporate abiotic factors, such as temperature and CO₂ concentration, into the mechanistic A_n-I curve model, as well as to determine the association between the abiotic factors and light harvesting pigment molecules, such as N_k, σ_ik', and τ_min.