Bioenergetic processes in guard cells related to stomatal function

Abstract

The energy required for ion uptake in guard cells is provided by two important bioenergetic processes, namely respiration and photosynthesis. The blue light-sensitive plasma membrane redox system is considered as the third bioenergetic phenomenon, since it uses blue light to create a proton gradient across the membrane. The unique features of respiration and photosynthesis in guard cells and their role in stomatal function are emphasized. Evidence for and against the blue light-sensitive components on plasma membrane (ATPase/distinct redox chain) and the photoreceptors (flavins, carotenoids, pterins) in guard cells are presented. The information on ion channels and their response to various kinds of secondary messengers including G-proteins, phosphoinositides, diacylglycerol, calcium, cAMP and protein kinases are reviewed. A model is presented indicating the possible mechanism of perception and transduction by guard cells of external signals and their interaction with different bioenergetic components.