Leaf Turgor Loss Does Not Coincide With Cell Plasmolysis in Drought-Tolerant Chaparral Species

Abstract

The water potential at which leaf cells lose turgor (Psi(TLP)) is a useful predictor of whole-plant drought tolerance and biome wetness. However, many plants can achieve water potential values below Psi(TLP) and recover, raising questions about the physiological processes that occur below Psi(TLP). We established a controlled greenhouse experiment to induce turgor loss on six shrub species from a Mediterranean-type ecosystem in Southern California and characterised physiological and leaf-structural adjustments to Psi(TLP). We documented seasonal adjustments in Psi(TLP), both with and without applied drought. Stomatal closure always occurred below Psi(TLP), and the margin between the two phenomena increased with lower Psi(TLP). Drought tolerance was strongly correlated with heat tolerance. Most histological responses to Psi(TLP) involved shrinkage of both spongy mesophyll cells and intercellular air spaces, leading to reduced leaf thickness, but not plasmolysis. Overall, our results indicate a propensity to reach Psi values far below Psi(TLP) and maintain function for extended periods of time in Southern California shrubs. Whereas species in many ecosystems fall below Psi(TLP) for brief periods of time, the erratic nature of precipitation patterns makes Southern California an outlier in the range of operational plant water potentials.

Keywords

chaparral; drought; heat; histology; thermal tolerance; turgor loss point

Published in

Plant, Cell and Environment
2025
Publisher: WILEY

SLU Authors

• Schönbeck, Leonie

  • Southern Swedish Forest Research Centre, Swedish University of Agricultural Sciences
    
  • University of California, Riverside (UCR)

UKÄ Subject classification

Botany

Publication identifier

• DOI: https://doi.org/10.1111/pce.15505

Permanent link to this page (URI)

https://res.slu.se/id/publ/141513