Form, Development and Function of Grass Stomata

Plants use sunlight to turn carbon dioxide (CO₂) and water into the sugars we eat and the oxygen we breathe. To take up CO₂ from the atmosphere land plants form microscopic “breathing” pores on their leaves, which are made up of two guard cells that can open and close and are called stomata (Greek for “mouths”). Land plants have evolved different stomatal morphologies with different gas exchange efficiencies. The grasses for example recruit two lateral subsidiary cells (or “helper cells”) that support the central guard cells to open and close faster. This is important for water use efficiency since open stomata not only take up CO₂ but also loose water vapor.

The Raissig Lab studies developmental, cytological and physiological aspects of different stomatal morphologies in land plants. We use genetic approaches like mutant screens and gene editing, (time-lapse) confocal microscopy, and physiological methods like infrared-based, leaf-level gas exchange measurements. Our lab works on the grass model Brachypodium distachyon that features physiologically superior four-celled stomata and the “go-to” model Arabidopsis thaliana with standard two-celled stomata. Furthermore, we are currently establishing novel model systems like Kalanchoë laxiflora with “intermediate” stomatal morphologies that maintain subsidiary-like cells around stomatal guard cells.

We hope to understand (1) how subsidiary cells are formed, (2) how they function to support stomatal gas exchange efficiency, and (3) how subsidiary cells have evolved.