Foliar water uptake via cork warts in mangroves of the Sonneratia genus

• Published in: Plant, cell and environment Vol. 44; no. 9; pp. 2925 - 2937
• Main Authors: Bryant, Callum, Fuenzalida, Tomas I., Zavafer, Alonso, Nguyen, Hoa T., Brothers, Nigel, Harris, Rosalie J., Beckett, Holly A. A., Holmlund, Helen I., Binks, Oliver, Ball, Marilyn C.
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.09.2021; Wiley Subscription Services, Inc
• Subjects: Dehydration; Dry season; Fluorescein; Halophytes; Kinetics; Leaves; Mangroves; pathway; Rainy season; Rehydration; sclereids; Seasonal variations; seasonality; Selectivity; Sonneratia; surface conductance; Surface water; Warts; Water potential; Water uptake; Wetting
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.14129

Foliar water uptake (FWU) occurs in plants of diverse ecosystems; however, the diversity of pathways and their associated FWU kinetics remain poorly resolved. We characterized a novel FWU pathway in two mangrove species of the Sonneratia genus, S. alba and S. caseolaris. Further, we assessed the influence of leaf wetting duration, wet‐dry seasonality and leaf dehydration on leaf conductance to surface water (Ksurf). The symplastic tracer dye, disodium fluorescein, revealed living cells subtending and encircling leaf epidermal structures known as cork warts as a pathway of FWU entry into the leaf. Rehydration kinetics experiments revealed a novel mode of FWU, with slow and steady rates of water uptake persistent over a duration of 12 hr. Ksurf increased with longer durations of leaf wetting and was greater in leaves with more negative water potentials at the initiation of leaf wetting. Ksurf declined by 68% between wet and dry seasons. Our results suggest that FWU via cork warts in Sonneratia sp. may be rate limited and under active regulation. We conclude that FWU pathways in halophytes may require ion exclusion to avoid uptake of salt when inundated, paralleling the capacity of halophyte roots for ion selectivity during water acquisition. Epidermal cork warts function as a pathway of foliar water uptake in the mangroves Sonneratia alba and S. caseolaris. Leaf surface conductance to water increased with leaf rehydration duration, was inhibited in the dry season and increased with leaf dehydration.