Xylem perforation plate phenotypes affect water use and drought adaptation in maize (Zea maysL.)

Abstract

Rationale: Xylem morphology in annual monocots is important for water use strategies in many agronomically important species. Methods: We assess how xylem perforation plates affect water use strategies in maize (Zea mays L.) through in silico modeling, empirical studies under water deficit in controlled environments, and in the field. Key Result: Significant genotypic variation for the prominence and frequency of perforation plates was observed in maize germplasm. Perforation plate phenotypes had high heritability, were associated with several QTL, and were pleiotropic across leaves, aerial nodal roots, and subterranean nodal roots. Perforation plate phenotypes did not affect vulnerability to cavitation, but modeling predicted that they should affect axial water transport, which was supported by in situ measurements of root segments. Metaxylem vessel length was correlated with the rate of root elongation, root depth, and deep-water utilization in mesocosms. Under drought stress in the field, variation in xylem vessel length was associated with leaf roll, leaf temperature, transpiration, photosynthesis, and grain yield. Main Conclusion: Phenotypic variation for xylem perforation plate phenotypes in maize directly affects axial water conductance and is part of a pleiotropic syndrome with greater root elongation and deeper rooting that improves adaptation to water deficit stress.