Improving Maize Water Use Efficiency: Strategies for Mitigating Water Demand Challenges in a Changing Environment

Improving Maize Water Use Efficiency: Strategies for Mitigating Water Demand Challenges in a Changing Environment Abstract Maize, a significant food source compared to other crops, has seen yield improvements due to genetic enhancements. However, to meet future demands, further enhancements are essential. Stagnant crop water use efficiency (WUE) poses a challenge to food security, emphasizing the importance of addressing inefficient crop water use. The current CO2 saturation in maize crop photosynthesis (Anet) offers a potential avenue for enhancing water use efficiency by genetically reducing stomatal conductance (gs). While this reduction in gs is anticipated to lower transpiration without impacting Anet, it simultaneously raises leaf temperature (Tleaf) and water vapor pressure deficits (VPD). Here, we use a mechanistic C4 leaf model (vLeaf) to explore the impact of gs reduction on leaf-level processes, revealing both direct effect (primary) and indirect feedback (secondary) of gs reduction on leaf WUE. Our simulations show that secondary effects can counteract the water-saving advantages derived from decreased transpiration, leading to a decline in WUE gains from 40% to 20%. Despite this notable decrease, it is important to highlight that these reductions do not nullify the WUE benefits associated with lowered gs. Moreover, simulations conducted under anticipated future conditions, characterized by elevated CO2 levels and drier air, indicate that a reduction of gs by 29% can yield WUE improvements of up to 28%. This study emphasizes the potential of reducing gs as an effective strategy to tackle the issue of water demand.