Scaling from leaf to crop canopy: Benefits of stomatal closure in soybean

Antriksh Srivastava, Venkatraman Srinivasan
Department of Civil Engineering, Indian Institute of Technology Madras, Chennai 600036, India

Soybean, one of the world’s four main staple crops, is an essential protein source. With rising water scarcity and climate change threats, improving water use efficiency (WUE) is crucial to sustain future yield increases. Decreasing stomatal conductance (gs) by manipulating stomatal size and density is a promising technique to enhance WUE. Here, the trade-off is improving WUE with minimal loss in photosynthesis (Anet). Presently, studies investigating gs reduction in C3 crops are confined to controlled environments and have shown mixed results regarding its benefits, while the effect of gs reduction in the field has not been tested. Using a mechanistic crop model (vCanopy), we predict the trade-offs of gs reduction in soybean under field conditions. Our simulations indicate that leaf-level gs reduction benefits are diminished due to energy balance feedback, which increases leaf temperature (Tleaf) and water vapour pressure deficit (VPD). Additionally, at the crop canopy level, gs reduction trade-offs are further diminished due to altered canopy scale mixing and longwave radiation, leading to increased canopy Tleaf and microenvironment VPD. Consequently, a 20% gs reduction results in a 19% water saving but also a 9% drop in Anet.