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

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

Over the past 60 years, advancements in genetics and agronomy have increased maize yields, while crop water use efficiency (WUE) has remained stagnant. Further yield increases will require more water unless WUE improves. Most research on improving crop WUE through stomatal conductance (gs) reduction has been focused on C3 crops, leaving the more suitable C4 crops largely unexplored. Additionally, gs reduction studies are typically conducted in controlled environments that do not reflect field conditions. Using a mechanistic crop model (vCanopy), we simulated the tradeoffs of gs reduction in maize crops under field conditions. Our findings show that energy balance feedbacks at the leaf and canopy levels diminish the benefits of gs reduction through increases in leaf temperature (Tleaf) and water vapour pressure deficit (VPD). However, gs reduction still results in beneficial tradeoffs in WUE with minimal loss in photosynthesis (Anet). Overall, a 24% drop in gs results in a 22% improvement in WUE without loss in Anet. Our results show that shaded and lower canopy leaves have higher WUE tradeoffs than sunlit and upper