Drought‐Induced Coordination of Photosynthesis, Stomata, and Hydraulics in Maize Leaves Between Sensitive and Tolerant Varieties

Identification of drought-tolerant maize varieties in the context of climate change is critical. Although many studies have reported that the coordination of stomatal and hydraulic conductance of plant leaves ensures the net photosynthetic rate, it is unclear whether the arrangement of these three parameters is consistent among maize varieties differing in drought tolerance. Therefore, in this study, gas exchange parameters, hydraulic properties, and stomatal structure of leaves from eight maize varieties under full and deficit irrigation (DI) were determined. Drought tolerance of varieties was assessed using principal component analysis, and the coordination of photosynthesis, stomatal and hydraulic conductance, as well as stomatal behavior was analyzed between drought-sensitive (DSVs) and drought-tolerant varieties (DTVs). Eight maize varieties were categorized into DSVs and DTVs based on the evaluation of these agronomic and physiological parameters. Significant variety-specific responses of physiological parameters to DI were found, with at least one parameter being significantly affected in each variety. Leaf net photosynthesis rate and stomatal conductance showed a tight coordination with hydraulic conductance among DSVs; however, this coordination was potentially absent among DTVs. Simulations of stomatal behavior based on Ball-Berry and Medlyn models showed that DI significantly reduced the model sensitivity parameters of m and g₁ regardless of DSVs and DTVs. The study highlights the importance of physiological trait coordination in drought responses. The coordination between stomatal and hydraulic traits may be absent in DTVs, implying a potentially flexible adaptation strategy that could be exploited to improve maize drought tolerance.