Most stomatal closure in woody species under moderate drought can be explained by stomatal responses to leaf turgo

13 páginas.-- 6 figuras.-- 93 referencias.-- Additional Supporting Informationmay be found in the online version of this article at the publisher’s web-site: http://dx.doi.org/10.1007/01407791

Reduced stomatal conductance (gs) during soil drought in angiosperms may result from effects of leaf turgor on stomata and/or factors that do not directly depend on leaf turgor, including root-derived abscisic acid (ABA) signals. To quantify the roles of leaf turgor-mediated and leaf turgor-independent mechanisms in gs decline during drought, we measured drought responses of gs and water relations in three woody species (almond, grapevine and olive) under a range of conditions designed to generate independent variation in leaf and root turgor, including diurnal variation in evaporative demand and changes in plant hydraulic conductance and leaf osmotic pressure. We then applied these data to a process-based gs model and used a novel method to partition observed declines in gs during drought into contributions from each parameter in the model. Soil drought reduced gs by 63-84% across species, and the model reproduced these changes well (r2=0.91, P<0.0001, n=44) despite having only a single fitted parameter. Our analysis concluded that responses mediated by leaf turgor could explain over 87% of the observed decline in gs across species, adding to a growing body of evidence that challenges the root ABA-centric model of stomatal responses to drought.

This work was funded by the Spanish Ministry of Science and innovation (research projects AGL2009-11310/AGR and AGL2012-34544/AGR) and co-funded by the FEDER programme. T.N.B. was supported by the National Science Foundation (award # 1146514) and the Australian Research Council (DP150103863 and LP130101183). C.M.R-D. benefited from an FPDI research fellowship from the Junta de Andalucía. We are grateful to A. Montero and A. Perez-Martin for assistance in the field.

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