Minimum conductance in leaves-cuticle, leaky stomata, or water vapor saturation?

Abstract

O_LIMinimum conductance (gw,min) in leaves is important for water relations in land plants. Yet, its regulation is unclear due to measurement constraints. C_LIO_LICuticle conductance to water vapor (gcw) was estimated from the difference between calculated and direct measurement of CO2 concentration in the leaf airspace (Ci) of amphi-stomatous tobacco and sunflower. We estimated gcw in a series of light and dark experiments, and partitioned gw,min into cuticle and stomatal components. Some leaves were detached to simulate severe drought through desiccation conditions where gw,min is generally determined. C_LIO_LIBetween light and dark experiments each gcw was in close agreement, and successfully corrected the discrepancies of calculations from direct measurements. In the dark, either stomatal or cuticle conductance dominated the gw,min, suggesting either of them can control the minimum water loss. In the detached leaves, gcw could not be estimated likely due to unsaturation in the leaf airspace, and gw,min was progressively underestimated. C_LIO_LIBesides cuticle, leaf water status is a potential pitfall of the standard gas exchange model. Our technique is useful to study the minimal gas exchange as well as to refine the model. C_LI

Plant phenotyping relevance

葉の最小コンダクタンスを分解・推定する測定技術を開発し、光・暗条件で検証しており、植物の生理形質取得が中心である。

Code and data availability

The supplied blocks contain no data availability, code deposit, or supplement statements; the paper describes gas-exchange experiments on tobacco and sunflower but provides no public dataset, images, code, or model assets with an authors' URL.

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