The impact of modifying photosystem antenna size on canopy photosynthetic efficiency—Development of a new canopy photosynthesis model scaling from metabolism to canopy level processes

Canopy photosynthesis (A_c) describes photosynthesis of an entire crop field and the daily and seasonal integrals of A_c positively correlate with daily and seasonal biomass production. Much effort in crop breeding has focused on improving canopy architecture and hence light distribution inside the canopy. Here, we develop a new integrated canopy photosynthesis model including canopy architecture, a ray tracing algorithm, and C₃ photosynthetic metabolism to explore the option of manipulating leaf chlorophyll concentration (Chl]) for greater A_c and nitrogen use efficiency (NUE). Model simulation results show that (a) efficiency of photosystem II increased when Chl] was decreased by decreasing antenna size and (b) the light received by leaves at the bottom layers increased when Chl] throughout the canopy was decreased. Furthermore, the modelling revealed a modest ~3% increase in A_c and an ~14% in NUE was accompanied when Chl] reduced by 60%. However, if the leaf nitrogen conserved by this decrease in leaf Chl] were to be optimally allocated to other components of photosynthesis, both A_c and NUE can be increased by over 30%. Optimizing Chl] coupled with strategic reinvestment of conserved nitrogen is shown to have the potential to support substantial increases in A_c, biomass production, and crop yields.