What are the evolutionary origins of stomatal responses to abscisic acid in land plants?

• Published in: Journal of integrative plant biology Vol. 59; no. 4; pp. 240 - 260
• Main Authors: Sussmilch, Frances C., Brodribb, Timothy J., McAdam, Scott A. M.
• Format: Journal Article
• Language: English
• Published: China (Republic : 1949- ) Wiley Subscription Services, Inc 01.04.2017; School of Biological Sciences, University of Tasmania, Hobart, Tasmania, Australia
• Subjects: Abscisic acid; Abscisic Acid - pharmacology; Active control; Angiospermae; Angiosperms; Aquatic plants; Biological Evolution; Bryophyta; Divergence; Embryophyta - physiology; embryophytes; Evolution; Leaves; Models, Biological; Plant Stomata - drug effects; Plant Stomata - physiology; Plants; Stomata; stomatal movement; Water deficit
• ISSN: 1672-9072; 1744-7909; 1744-7909
• DOI: 10.1111/jipb.12523

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. This review examines when active, ABA‐mediated mechanisms for control of stomatal aperture evolved in land plants, allowing improved plant survival in dry terrestrial environments. The evidence for two prominent and opposing models is outlined with recent findings strongly supporting the gradual evolution of ABA‐driven control from passive ancestral responses.