Modeling light response of effective quantum efficiency of photosystem II for C and C crops.

Effective quantum efficiency of photosystem II (Φ) represents the proportion of photons of incident light that are actually used for photochemical processes, which is a key determinant of crop photosynthetic efficiency and productivity. A robust model that can accurately reproduce the nonlinear light response of Φ (Φ-) over the I range from zero to high irradiance levels is lacking. In this study, we tested a Φ- model based on the fundamental properties of light absorption and transfer of energy to the reaction centers via photosynthetic pigment molecules. Using a modeling-observation intercomparison approach, the performance of our model versus three widely used empirical Φ- models were compared against observations for two C crops (peanut and cotton) and two cultivars of a C crop (sweet sorghum). The results highlighted the significance of our model in (1) its accurate and simultaneous reproduction of light response of both Φ and the photosynthetic electron transport rate () over a wide I range from light limited to photoinhibition levels and (2) accurately returning key parameters defining the light response curves.