Canopy photosynthesis is the integral of photosynthesis of all the above ground parts of plant canopy. Canopy photosynthetic efficiency is a major determinant to biomass production and crop yield potential. The microclimate and photosynthetic properties of different leaves in a canopy are largely different and dynamic. To study canopy photosynthesis, we developed 3D canopy model and ray tracing algorithm for calculating canopy photosynthesis. With 3D model, we dissected the contributions of plant architectural, physiological and environmental factors to canopy photosynthesis. Currently, we have developed models of maize, rice, wheat and soybean. We also developed canopy gas exchange system (CAPTS) and high throughput phenomics platform for measuring canopy photosynthesis related traits. With CAPTS system, canopy photosynthesis rate of wheat grown in field was measured. We quantified the dynamic changes of crop canopy light use efficiency (LUE), energy conversion efficiency (ec) during a day and a growing season with canopy gas exchange method. Results show that the LUE of two wheat cultivars with different canopy architectures at five stages varies between 0.01 to about 0.05 mol CO2 mol-1 photon, with the LUE being higher under medium PAR. Throughout the growing season, the ec varies from 0.5% to 3.7% (11%~80% of the maximal ec for C3 plants) with incident PAR identified as a major factor controlling variation of ec. The estimated average ec from tillering to grain filling stages was about 2.17%, i.e. 47.2% of the theoretical maximal. The estimated season-averaged radiation use efficiency (RUE) was 1.5~1.7 g MJ-1, which was similar to the estimated RUE based on biomass harvesting. The large variations of LUE and ec imply great opportunity to improve canopy photosynthesis for greater wheat biomass and yield potential.
Audience Take Away:
- New research tools for plant canopy photosynthesis
- New canopy models and methods used for studying canopy photosynthesis
- Combination of plant phenomics technology and 3D plant modeling