Water exchange between the Chlorenchyma and the Hydrenchyma and its physiological role in leaves with Crassulacean acid metabolism

Abstract

Direct and non‐destructive measurements of plant‐water relations of plants exhibiting the Crassulacean acid metabolism (CAM) photosynthetic pathway are seldom addressed, with most findings inferred from gas exchange measurements. The main focus of this paper was to study how the water exchange between the chlorenchyma and the hydrenchyma depends on and follows the CAM photosynthetic diel pattern using non‐invasive and continuous methods. Gas exchange and leaf patch clamp pressure probe (LPCP) measurements were performed on Aloe vera (L.) Burm f., a CAM species, and compared to measurements on banana (Musa acuminata Colla), a C₃ species. The LPCP output pressure, Pₚ, of Aloe vera plants follows its diel CAM photosynthetic cycle, reversed to that observed in banana and other C₃ species. The four phases of CAM photosynthesis can also be identified in the diel LPCP output pressure, Pₚ, cycle. The Pₚ values in Aloe vera are determined by the hydrenchyma turgor pressure, with both parameters being reversely related. A non‐invasive and continuous assessment of the water exchange between the chlorenchyma and the hydrenchyma in CAM plants, namely, by following the changes in the hydrenchyma turgor pressure, is presented. However, showing once more how the LPCP output pressure, Pₚ, depends on the leaf structure, such an approach can be used to study plant‐water relations in other CAM species with a leaf structure similar to Aloe vera, with the hydrenchyma composing most of the leaf volume.

Plant phenotyping relevance

LPCPを用いた非侵襲・連続的な葉内水分交換／ハイドレンキマの膨圧測定を中心に、CAM植物の水分状態を評価する方法を提示・適用しているため。

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