title: Leaf gas exchange performance and the lethal water potential of five European species during drought.
abstract: Establishing physiological thresholds to drought-induced mortality in a range of plant species is crucial in understanding how plants respond to severe drought. Here, five common European tree species were selected (Acer campestre L., Acer pseudoplatanus L., Carpinus betulus L., Corylus avellana L. and Fraxinus excelsior L.) to study their hydraulic thresholds to mortality. Photosynthetic parameters during desiccation and the recovery of leaf gas exchange after rewatering were measured. Stem vulnerability curves and leaf pressure-volume curves were investigated to understand the hydraulic coordination of stem and leaf tissue traits. Stem and root samples from well-watered and severely drought-stressed plants of two species were observed using transmission electron microscopy to visualize mortality of cambial cells. The lethal water potential (ψlethal) correlated with stem P99 (i.e., the xylem water potential at 99% loss of hydraulic conductivity, PLC). However, several plants that were stressed beyond the water potential at 100% PLC showed complete recovery during the next spring, which suggests that the ψlethal values were underestimated. Moreover, we observed a 1 : 1 relationship between the xylem water potential at the onset of embolism and stomatal closure, confirming hydraulic coordination between leaf and stem tissues. Finally, ultrastructural changes in the cytoplasm of cambium tissue and mortality of cambial cells are proposed to provide an alternative approach to investigate the point of no return associated with plant death.
authors.affiliation: Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany.
authors.forename: Shan
authors.initials: S
authors.lastname: Li
authors.affiliation: Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany.
authors.forename: Marion
authors.initials: M
authors.lastname: Feifel
authors.affiliation: Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany Department of Biology, Faculty of Science, Golestan University, 36154 Gorgan, Iran.
authors.forename: Zohreh
authors.initials: Z
authors.lastname: Karimi
authors.affiliation: Plant Ecology, Albrecht von Haller Institute for Plant Sciences, University of Göttingen, D-37077 Göttingen, Germany.
authors.forename: Bernhard
authors.initials: B
authors.lastname: Schuldt
authors.affiliation: University of Western Sydney, Hawkesbury Institute for the Environment, Richmond, NSW 2753, Australia.
authors.forename: Brendan
authors.initials: B
authors.lastname: Choat
authors.affiliation: Institute for Systematic Botany and Ecology, Ulm University, D-89081 Ulm, Germany steven.jansen@uni-ulm.de.
authors.forename: Steven
authors.initials: S
authors.lastname: Jansen
mesh_terms: D031002:Acer / Q000502:physiology; D029401:Betulaceae / Q000502:physiology; D003890:Desiccation; D055864:Droughts; D005060:Europe; D031661:Fraxinus / Q000502:physiology; D010788:Photosynthesis; D018515:Plant Leaves / Q000502:physiology; D014197:Trees / Q000502:physiology*
keywords: cambium vitality; embolism resistance; hydraulic failure; leaf turgor; photosynthesis; plant death; xylem water potential