Stomatal dynamics are limited by leaf hydraulics in ferns and conifers: results from simultaneous measurements of liquid and vapour fluxes in leaves

• Published in: Plant, cell and environment cell and environment, 2016-03, Vol.39 (3), p.694-705
• Main Authors: Martins, Samuel C. V, McAdam, Scott A. M, Deans, Ross M, DaMatta, Fábio M, Brodribb, Tim J
• Format: Article
• Language: English
• Subjects: capacitance; carbon; conifers; Ferns - anatomy & histology; Ferns - physiology; ferns and fern allies; gas exchange; Leaf capacitance; leaf hydraulic conductance; leaf water content; leaves; Magnoliophyta; Models, Biological; Plant Stomata - physiology; Steam; stomata; stomatal conductance; stomatal movement; Time Factors; vapor pressure; vapors; vapour pressure deficit; water balance
• ISSN: 0140-7791; 1365-3040
• DOI: 10.1111/pce.12668

Stomatal responsiveness to vapour pressure deficit (VPD) results in continuous regulation of daytime gas‐exchange directly influencing leaf water status and carbon gain. Current models can reasonably predict steady‐state stomatal conductance (gₛ) to changes in VPD but the gₛ dynamics between steady‐states are poorly known. Here, we used a diverse sample of conifers and ferns to show that leaf hydraulic architecture, in particular leaf capacitance, has a major role in determining the gₛ response time to perturbations in VPD. By using simultaneous measurements of liquid and vapour fluxes into and out of leaves, the in situ fluctuations in leaf water balance were calculated and appeared to be closely tracked by changes in gₛ thus supporting a passive model of stomatal control. Indeed, good agreement was found between observed and predicted gₛ when using a hydropassive model based on hydraulic traits. We contend that a simple passive hydraulic control of stomata in response to changes in leaf water status provides for efficient stomatal responses to VPD in ferns and conifers, leading to closure rates as fast or faster than those seen in most angiosperms.