Abstract
Canopy photosynthesis (Ac) describes photosynthesis of an entire crop field and the daily and seasonal integrals of Ac 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 Ac 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 Ac 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 Ac 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 Ac, biomass production, and crop yields.
Highlights
Canopy photosynthesis (Ac) describes photosynthesis of both top and bottom layer leaves
Considering that modifying leaf chlorophyll concentration mainly influences leaf photosynthesis through modifying light environments inside a canopy, we studied the potential impacts of different canopy architecture and growth latitudes on the benefits of modifying leaf chlorophyll concentration on canopy photosynthesis (Ac)
This paper reports development of a dynamic systems model of canopy photosynthesis and its application in exploring the potential of decreasing leaf chlorophyll concentration as a strategy to improve canopy photosynthetic CO2 uptake rates for canopies with a variety of architectural features and grown under different latitudes
Summary
Canopy photosynthesis (Ac) describes photosynthesis of both top and bottom layer leaves. By combining with evolutionary algorithms, we are able to explore the optimal nitrogen distribution into different enzymes of photosynthetic carbon metabolism to maximize photosynthesis Combining this advanced dynamic leaf photosynthesis model with modelling of the heterogeneous light environment within canopies enables prediction of dynamic changes of canopy photosynthesis in any canopy of defined architecture. We have assembled an integrated canopy photosynthesis model by combining canopy architecture model (Song et al, 2013), ray tracing algorithm (Song et al, 2013), photo‐acclimation model (Hikosaka & Terashima, 1995; Kull & Kruijt, 1999; Moreau et al, 2012), and dynamic systems model of C3 leaf photosynthesis (Zhu et al, 2013) Using this model, we have systematically evaluated the effects of reducing leaf chlorophyll concentration to light and nitrogen use efficiencies of a rice canopy
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