The evolution of active stomatal closure in response to leaf water deficit, mediated by the hormone abscisic acid (ABA), has been the subject of recent debate. Two different models for the timing of the evolution of this response recur in the literature. A single-step model for stomatal control suggests that stomata evolved active, ABA-mediated control of stomatal aperture, when these structures first appeared, prior to the divergence of bryophyte and vascular plant lineages. In contrast, a gradualistic model for stomatal control proposes that the most basal vascular plant stomata responded passively to changes in leaf water status. This model suggests that active ABA-driven mechanisms for stomatal responses to water status instead evolved after the divergence of seed plants, culminating in the complex, ABA-mediated responses observed in modern angiosperms. Here we review the findings that form the basis for these two models, including recent work that provides critical molecular insights into resolving this intriguing debate, and find strong evidence to support a gradualistic model for stomatal evolution.

Item Type:	Refereed Article
Keywords:	evolution, stomatal responses, abscisic acid, land plants
Research Division:	Biological Sciences
Research Group:	Plant Biology
Research Field:	Plant Physiology
Objective Division:	Expanding Knowledge
Objective Group:	Expanding Knowledge
Objective Field:	Expanding Knowledge in the Environmental Sciences
Author:	Sussmilch, FC (Dr Frances Sussmilch)
Author:	Brodribb, TJ (Professor Tim Brodribb)
Author:	McAdam, SAM (Dr Scott McAdam)
ID Code:	117162
Year Published:	2017
Funding Support:	Australian Research Council (DP140100666)
Web of Science® Times Cited:	9
Deposited By:	Plant Science
Deposited On:	2017-06-01
Last Modified:	2018-08-02
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