Ionic relations of stomatal movement and signal transduction in guard cells

Abstract

A variety of different hypotheses have been put forward over the last century and a half to explain how stomata open and close (see Chapter 1). All have proved inadequate to a greater or lesser degree. Since the late 1960S, however, major advances in our understanding of how stom- ata function have been made with the application of diverse and new technologies, such as electrophysiology and ion imaging. It is now clear that ion accumulation forms a major part of the osmotic increases observed during stomatal opening and recent experiments have started to link control of ion movement with transduction of physiological stim- uli. The conceptual framework for signal transduction relies heavily on models derived from animal cell systems, although sufficient data is beginning to accumulate to establish interactions in the signalling net- work that are unique to guard cells. In this chapter the mechanisms leading to reversible ion accumulation and release by guard cells are considered, followed by a discussion of how such ion fluxes are regu- lated by internal and external signals.