Přednáška z Anatomie a fyziologie rostlin

datum 13.12.2001
přednáší Prof. Rainer Hedrich (Institute for Molecular Plant Physiology and Biophysics, University of Wuerzburg, Německo)
název Ion channels help plants saving water
anotace Stomata, microscopic pores in the epidermis of plants, are surrounded by a pair of guard cells. Turgor changes in these cells can open or close the stomata to balance the uptake of CO2 from the atmosphere and the concomitant loss of water from leaves. Drought signal-induced K+ salt release decreases guard cell turgor and volume which in turn leads to stomatal closure, reducing transpiration loss. Chloride, nitrate, and malate are the primary anions that counterbalance the fluxes of K+ during stomatal movement. In the seminar the nature and biology of guard cell ion channels will be addressed.

Arabidopsis mutants and characterization of anion channels heterologously expressed in animal cells indicated that they are controlled by a distinct set of protein kinases and phosphatases addressed by the water stress hormone ABA. Binding of ABA to this receptor-phosphatase complex inhibits the activity of the phosphatase. With the phosphatase blocked the kinase phosphorylated the anion channels. When gated open anion release depolarizes the membrane and activates the potassium-release channel. Concerted loss of osmolites deflates guard cells giving rise to stomata closure and thus termination of transpiration when water supply is limited.
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