Optimizing canopy photosynthetic rate through PAR modeling in cotton (Gossypium spp.) crops

Abstract

A study of the distribution of photosynthetically active radiation (PAR) within cotton (Gossypium spp.) canopies of varying architecture is presented. Based on this study, a computer model is formulated to estimate PAR distribution and photosynthetic rates of cotton canopies. The model is developed from photon flux densities (PFD) measured at several stages of development in row-planted cotton canopies. The photon transport equation is implemented into the model along with an algorithm to calculate canopy photosynthetic rates. The resulting model is then used to generate different scenarios of plant architecture to identify the canopy architecture with optimal canopy photosynthetic rates.The results demonstrate that the differences in light distribution within the different cotton canopies were successfully captured. The model reproduces PAR distributions successfully for the cotton cultivars included in the study (R2>0.9 for most cultivars).Photosynthetic rate estimations showed that the structure of the DP-50 canopy is the most efficient canopy architecture by allowing PAR penetration throughout its canopy. This cultivar also uses the available sunlight more efficiently by enhancing PAR interception. The optimization process suggests that a cotton plant could increase its photosynthetic rate by 10% by distributing leaves within the canopy similarly to that of DP-50, and with leaves shaped like small-to-medium PS-6 leaves.