Plumbing the depths: extracellular water storage in specialized leaf structures and its functional expression in a three‐domain pressure –volume relationship. (25th July 2016)

• Record Type: Journal Article
• Authors: Nguyen, Hoa T.; Meir, Patrick; Wolfe, Joe; Mencuccini, Maurizio; Ball, Marilyn C.
• Is Part Of: Plant, cell and environment. Volume 40:Number 7(2017)
• Page Start: 1021
• Page End: 1038
• Publication Date: 2016-07-25
• Subjects: cisternae -- dehydration -- leaf water capacitance -- mangrove -- plasmolysis -- PV curve -- trichomes; Plant physiology -- Periodicals; Plant cells and tissues -- Periodicals; Plant communities -- Periodicals; 581.105
• DOI: 10.1111/pce.12788
• Languages: English
• ISSNs: 0140-7791

Abstract

Abstract: A three‐domain pressure–volume relationship (PV curve) was studied in relation to leaf anatomical structure during dehydration in the grey mangrove, Avicennia marina . In domain 1, relative water content (RWC) declined 13% with 0.85 MPa decrease in leaf water potential, reflecting a decrease in extracellular water stored primarily in trichomes and petiolar cisternae. In domain 2, RWC decreased by another 12% with a further reduction in leaf water potential to −5.1 MPa, the turgor loss point. Given the osmotic potential at full turgor (−4.2 MPa) and the effective modulus of elasticity (~40 MPa), domain 2 emphasized the role of cell wall elasticity in conserving cellular hydration during leaf water loss. Domain 3 was dominated by osmotic effects and characterized by plasmolysis in most tissues and cell types without cell wall collapse. Extracellular and cellular water storage could support an evaporation rate of 1 mmol m −2 s −1 for up to 54 and 50 min, respectively, before turgor loss was reached. This study emphasized the importance of leaf anatomy for the interpretation of PV curves, and identified extracellular water storage sites that enable transient water use without substantive turgor loss when other factors, such as high soil salinity, constrain rates of water transport. Abstract : The pressure‐volume relationships in field grown leaves of the mangrove, Avicennia marina, exhibited three domains dominated successively by 1) the presence and consumption of extracellular water, 2) variable turgor and loss of intracellular water, and 3) osmotic behavior of flaccid cells and plasmolysis. Multiple sites of extracellular water storage were identified, including hollow trichomes and novel structures named "cisternae". When fully charged, extracellular and cellular water storage could support a typical evaporation rate of 1 mmol m −2 s −1 for 54 and 50 min, respectively, before turgor loss was reached. This study emphasizes the importance of leaf anatomy for the interpretation of PV curves, and identifies extracellular water storage sites that enable transient water use without substantive turgor loss when other factors, such as high soil salinity, constrain rates of water transport.