Coordination of stomata and vein patterns with leaf width underpins water‐use efficiency in a C<sub>4</sub> crop
Ling Pan, Barbara George‐Jaeggli, Andrew Borrell, David Jordan, Fiona Koller, Yazen Al‐Salman, Oula Ghannoum, Francisco Javier Cano
Abstract
Abstract Despite its importance for crop water use and productivity, especially in drought‐affected environments, the underlying mechanisms of variation in intrinsic water‐use efficiency ( iWUE = net photosynthesis/stomatal conductance for water vapour, g sw ) are not well understood, especially in C 4 plants. Recently, we discovered that leaf width ( LW ) correlated negatively with iWUE and positively with g sw across several C 4 grasses. Here, we confirmed these relationships within 48 field‐grown genotypes differing in LW in Sorghum bicolor , a C 4 crop adapted to dry and hot conditions. We measured leaf gas exchange and modelled leaf energy balance three times a day, alongside anatomical traits as potential predictors of iWUE . LW correlated negatively with iWUE and stomatal density, but positively with g sw , interveinal distance of longitudinal veins, and the percentage of stomatal aperture relative to maximum. Energy balance modelling showed that wider leaves needed to open their stomata more to generate a more negative leaf‐to‐air temperature difference, especially at midday when air temperatures exceeded 40°C. These results highlight the important role that LW plays in shaping iWUE through coordination of vein and stomatal traits and by affecting stomatal aperture. Therefore, LW could be used as a predictor of higher iWUE among sorghum genotypes.