Review: Role of blue and red light in stomatal dynamic behaviour (J Exp Bot)

Guard cells are extremely sensitive and dynamic, and their behaviour controls rates of gas exchange and transpiration, which affect evaporative cooling and transport in the xylem. Matthews et al. review the roles of light signalling pathways in guard cell responses. Cues that control guard cell ion channels and transporters (hence stomatal pore size) include temperature, CO₂ and vapor-pressure deficit, as well as both blue and red light. The blue-light response is mediated by phototropins, whereas the red-light response is a consequence of photosynthesis in the guard cells and mesophyll cells, mediated by changes in the concentrations of CO₂ , ATP, sugars, and other metabolites. In some situations, the blue light response increases transpiration without increasing photosynthesis, so tuning guard cell responses to different wavelengths of light might be a way to improve water-use efficiency or cooling, as described in the article. (Summary by Mary Williams) J. Exp. Bot. 10.1093/jxb/erz563