A pleiotropic “stretch” phenotype is associated with metaxylem vessel element length, axial hydraulic conductance, root elongation, water utilization, and drought adaptation in maize

Abstract We tested the hypothesis that metaxylem phenotypes influence drought adaptation in maize ( Zea mays L.) through in silico modeling and empirical studies under water deficit in controlled environments and in the field. Substantial genotypic variation for metaxylem vessel element length (MVEL) was observed. Longer MVEL was correlated with reduced xylem perforation plate height, greater vessel length, and greater axial hydraulic conductance in silico, which was supported by in situ measurements of root segments. Genome‐wide association study revealed two different significant single nucleotide polymorphisms associated with MVEL and perforation plate height. Longer MVEL was correlated with greater root elongation, root depth, and deep water utilization in mesocosms. Under drought stress in the field, MVEL was associated with leaf roll, leaf temperature, transpiration, photosynthesis, and grain yield. We conclude that variation for MVEL in maize affects axial hydraulic conductance and is part of a pleiotropic syndrome we term the “stretch phenotype” with greater root elongation and deeper rooting that improves adaptation to water deficit stress.