Stomatal conductance reduction tradeoffs in maize leaves: A theoretical study

As the leading global grain crop, maize significantly impacts agricultural water usage. Presently, photosynthesis ((Formula presented.)) in leaves of modern maize crops is saturated with (Formula presented.), implying that reducing stomatal conductance ((Formula presented.)) would not affect (Formula presented.) but reduce transpiration ((Formula presented.)), thereby increasing water use efficiency (WUE). While (Formula presented.) reduction benefits upper canopy leaves under optimal conditions, the tradeoffs in low light and nitrogen-deficient leaves under nonoptimal microenvironments remain unexplored. Moreover, (Formula presented.) reduction increases leaf temperature ((Formula presented.)) and water vapor pressure deficit, partially counteracting transpiratory water savings. Therefore, the overall impact of (Formula presented.) reduction on water savings remains unclear. Here, we use a process-based leaf model to investigate the benefits of reduced (Formula presented.) in maize leaves under different microenvironments. Our findings show that increases in (Formula presented.) due to (Formula presented.) reduction can diminish WUE gains by up to 20%. However, (Formula presented.) reduction still results in beneficial WUE tradeoffs, where a 29% decrease in (Formula presented.) in upper canopy leaves results in a 28% WUE gain without loss in (Formula presented.). Lower canopy leaves exhibit superior tradeoffs in (Formula presented.) reduction with 178% gains in WUE without loss in (Formula presented.). Our simulations show that these WUE benefits are resilient to climate change.