On Guard

On Guard

By Christophe Benning

Guard cell photosynthesis is critical for stomatal turgor production, yet does not directly mediate CO2- and ABA-induced stomatal closing.

Tamar Azoulay-Shemer, Axxell Palomares, Andisheh Bagheri, Maria Israelsson-Nordstrom, Cawas B. Engineer, Bastiaan O. R. Bargmann, Aaron B. Stephan and Julian I. Schroeder The Plant Journal 83(4): 567–581.Article first published online: 22 JUL 2015 | DOI: 10.1111/tpj.12916

Photosynthesis drives live on earth and is a function of chloroplasts within green tissues of plants. In the process sunlight is converted into chemical energy and CO2 is chemically reduced and converted into the building blocks of plant cells. Stomata mediate the gas exchange between the inter-cellular spaces of leaves and the atmosphere. CO2 levels in leaves (Ci) are determined by respiration, photosynthesis, stomatal conductance and atmospheric [CO2]. [CO2] in leaves mediates stomatal movements. The role of guard cell photosynthesis in stomatal conductance responses is a matter of debate, and genetic approaches are needed.

To investigate the role of photosynthesis in stomata, Schroeder and his colleagues generated and analyzed transgenic plants that lack chlorophyll specifically in guard cells. The results provide genetic evidence that CO2/ABA-induced stomatal closure is nf the stomata in these lines are deflated showing a previously not-described ‘thin-shaped’ stomatal morphology, which suggests a key function of guard cell photosynthesis for energization and turgor production of stomatal guard cells.