Ancestral stomatal control results in a canalization of fern and lycophyte adaptation to drought

• Published in: The New phytologist Vol. 198; no. 2; pp. 429 - 441
• Main Authors: McAdam, Scott A. M., Brodribb, Timothy J.
• Format: Journal Article
• Language: English
• Published: England New Phytologist Trust 01.04.2013; Wiley Subscription Services, Inc
• Subjects: Abscisic acid; abscisic acid (ABA); Abscisic Acid - pharmacology; Adaptation, Physiological - drug effects; Atmosphere; Atmospheric water; Capacitance; Constraints; Dehydration; Desiccation; Drought; Droughts; Ferns; Ferns - drug effects; Ferns - physiology; Hormones; Humidity; Leaves; lycophytes; Photosynthesis; Plant ecology; Plant Stomata - drug effects; Plant Stomata - physiology; Plants; Population ecology; Rainforests; Soil; Soil stresses; Soil water; Soils; Species; Species diversity; Species Specificity; Stomata; Survival; Vapor Pressure; vapour pressure deficit; Water - metabolism; Water deficit; Water potential; Water stress; Water use
• ISSN: 0028-646X; 1469-8137
• DOI: 10.1111/nph.12190

Little is known about how a predominantly passive hydraulic stomatal control in ferns and lycophytes might impact water use under stress. Ferns and lycophytes occupy a diverse array of habitats, from deserts to rainforest canopies, raising the question of whether stomatal behaviour is the same under all ecological strategies and imposes ecological or functional constraints on ferns and lycophytes. We examined the stomatal response of a diverse sample of fern and lycophyte species to both soil and atmospheric water stress, assessing the foliar level of the hormone abscisic acid (ABA) over drought and recovery and the critical leaf water potential (Ψl) at which photosynthesis in droughted leaves failed to recover. The stomata of all ferns and lycophytes showed very predictable responses to soil and atmospheric water deficit via Ψl, while stomatal closure was poorly correlated with changes in ABA. We found that all ferns closed stomata at very low levels of water stress and their survival afterwards was limited only by their capacitance and desiccation tolerance. Ferns and lycophytes have constrained stomatal responses to soil and atmospheric water deficit as a consequence of a predominantly passive stomatal regulation. This results in a monotypic strategy in ferns and lycophytes under water stress.