Localized measurements of water potential reveal large loss of conductance in living tissues of maize leaves

Abstract

The water status of the living tissue in leaves between the xylem and stomata (outside xylem zone - OXZ) play a critical role for plant function and global mass and energy balance but has remained largely inaccessible. We resolve the local water relations of OXZ tissue using a nanogel reporter of water potential ({psi}), AquaDust, that enables an in-situ, non-destructive measurement of both{psi} of xylem and highly localized{psi} at the terminus of transpiration in the OXZ. Working in maize, these localized measurements reveal gradients in the OXZ that are several fold larger than those based on conventional methods, and values of{psi} in the mesophyll apoplast well below the macroscopic turgor loss potential. We find a strong loss of hydraulic conductance in both the bundle sheath and the mesophyll with decreasing xylem potential but not with evaporative demand. Our measurements suggest an active role played by the OXZ in regulating the transpiration path and our methods provide novel means to study this phenomenon.

Plant phenotyping relevance

AquaDustを用いた葉内の局所的な水ポテンシャル測定法が研究の中心であり、植物の水状態・水理特性を定量化している。

Code and data availability

The supplied blocks contain no public phenotype/trait datasets, imaging/sensor inputs, author analysis code, or trained models with explicit availability statements or URLs. The paper describes AquaDust water-potential measurements in maize leaves, but no data or code deposit is mentioned; only a patent declaration and

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