Abstract
Leaves of higher terrestrial plants have small pores — stomata — responsible for gas exchange. The opening of each stoma results from the osmotic uptake of water by two specialised cells — the guard cells. Because of the involvement in this mechanism of ATPase-proton pumps and active transport of ions across membranes, we have designed an Exploring Guard Cell Movement activity for biology teachers to provide a practical approach to some relevant aspects of bioenergetics and plant physiology.