AUTHOR=Habermann Eduardo , Dias de Oliveira Eduardo A. , Contin Daniele Ribeiro , San Martin Juca A. B. , Curtarelli Lucas , Gonzalez-Meler Miquel A. , Martinez Carlos Alberto 

TITLE=Stomatal Development and Conductance of a Tropical Forage Legume Are Regulated by Elevated [CO2] Under Moderate Warming

JOURNAL=Frontiers in Plant Science

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2019.00609

DOI=10.3389/fpls.2019.00609

ISSN=1664-462X

ABSTRACT=<p>The opening and closing of stomata are controlled by the integration of environmental and endogenous signals. Here, we show the effects of combining elevated atmospheric carbon dioxide concentration (<italic>eCO</italic><sub>2</sub>; 600 μmol mol<sup>-1</sup>) and warming (+2°C) on stomatal properties and their consequence to plant function in a <italic>Stylosanthes capitata</italic> Vogel (C<sub>3</sub>) tropical pasture. The <italic>eCO</italic><sub>2</sub> treatment alone reduced stomatal density, stomatal index, and stomatal conductance (<italic>g<sub>s</sub></italic>), resulting in reduced transpiration, increased leaf temperature, and leading to maintenance of soil moisture during the growing season. Increased CO<sub>2</sub> concentration inside leaves stimulated photosynthesis, starch content levels, water use efficiency, and PSII photochemistry. Under warming, plants developed leaves with smaller stomata on both leaf surfaces; however, we did not see effects of warming on stomatal conductance, transpiration, or leaf water status. Warming alone enhanced PSII photochemistry and photosynthesis, and likely starch exports from chloroplasts. Under the combination of warming and <italic>eCO</italic><sub>2</sub>, leaf temperature was higher than that of leaves from the warming or <italic>eCO</italic><sub>2</sub> treatments. Thus, warming counterbalanced the effects of CO<sub>2</sub> on transpiration and soil water content but not on stomatal functioning, which was independent of temperature treatment. Under warming, and in combination with <italic>eCO</italic><sub>2</sub>, leaves also produced more carotenoids and a more efficient heat and fluorescence dissipation. Our combined results suggest that control on stomatal opening under <italic>eCO</italic><sub>2</sub> was not changed by a warmer environment; however, their combination significantly improved whole-plant functioning.</p>