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The stomatal physiology of calcicoles in relation to calcium delivered in the xylem sap.

Research output: Contribution to journalJournal article

Published

Journal publication date22/07/1994
JournalProceedings of the Royal Society B: Biological Sciences
Journal number1348
Volume257
Number of pages5
Pages81-85
Original languageEnglish

Abstract

Physiological mechanisms in calcicoles in simulated highly calcareous habitats have been investigated using Campanula glomerata, Centaurea scabiosa and Leontodon hispidus. Diffusion resistance of the leaves was unaffected by high concentrations (15 mol m-3) of rhizospheric calcium in all three species, and in C. scabiosa and L. hispidus there was no inhibition of leaf extension even at 20 mol m-3. Free calcium concentrations in samples of xylem sap taken from the roots were found to be very close to those in the rhizosphere. However, stomata on isolated epidermis of C. scabiosa and L. hispidus closed in response to elevated free calcium in the same manner as those of Commelina communis, a calcium-neutral plant. It is concluded that the calcicoles must possess an efficient mechanism to remove high concentrations of free calcium delivered into the leaf's apoplast by the transpiration stream. If the xylem sap reached the apoplast around the stomata containing even 5-10% of its free calcium, stomatal function would be disturbed. If these species are representative of calcicoles in general, the leaf's mechanism for preventing excess calcium from reaching the stomatal guard cells may be indispensable. The capacity to remove or sequester most of the calcium delivered in the xylem may be a key factor in determining whether a plant is a calcicole or not.