Molecular approaches to leaf guard cells

Stomatal guard cells are highly differentiated cell types within the epidermis of higher plant leaves. These cells are intimately involved in regulating gas exchange, i.e. the release of water and the uptake of CO2, through the leaf surface. Guard cells represent an interesting cell type since they respond to various plant internal (e.g. hormones) and external (e.g. humidity, light, CO2) signals in a relatively simple manner. Stomatal pore size is changed by modulating the level of osmotically active compounds within the guard cells. In the past, guard cells have mainly been studied using electrophysiological, biochemical and whole-plant techniques. Only recently molecular techniques have been applied to address questions regarding control mechanisms of stomatal functioning. In the following a short overview is given on these molecular approaches.