A relook into plant wilting: observational evidence based on unsaturated soil-plant-photosynthesis interaction.

Abstract

Permanent wilting point (PWP) is generally used to ascertain plant resistance against abiotic drought stress and designated as the soil water content (θ) corresponding to soil suction (ψ) at 1500 kPa obtained from the soil water retention curve. Determination of PWP based on only pre-assumed ψ may not represent true wilting condition for soils with contrasting water retention abilities. In addition to ψ, there is a need to explore significance of additional plant parameters (i.e., stomatal conductance and photosynthetic status) in determining PWP. This study introduces a new framework for determining PWP by integrating plant leaf response and ψ during drought. Axonopus compressus were grown in two distinct textured soils (clayey loam and silty sand), after which drought was initiated till wilting. Thereafter, ψ and θ within the root zone were measured along with corresponding leaf stomatal conductance and photosynthetic status. It was found that coarse textured silty sand causes wilting at much lower ψ (≈ 300 kPa) than clayey loam (≈ 1600 kPa). Plant response to drought was dependent on the relative porosity and mineralogy of the soil, which governs the ease at which roots can grow, assimilate soil O 2 , and uptake water. For clay loam, the held water within the soil matrix does not facilitate easy root water uptake by relatively coarse root morphology. Contrastingly, fine root hair formation in silty sand facilitated higher plant water uptake and doubled the plant survival time.

Plant phenotyping relevance

植物の萎凋点を、土壌水分ポテンシャルだけでなく葉の気孔コンダクタンスと光合成状態を統合して判定する新しい枠組みを提案しており、植物状態の取得・評価法が研究の中心です。

Code and data availability

The article describes greenhouse column experiments measuring soil suction, water content, stomatal conductance, and photosynthetic parameters, but the supplied blocks contain no data availability statement, no public dataset deposit, no author code/scripts, and no trained models or checkpoints. Only the Creative CC-BY

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