PLANT-GROWTH HORMONES CONTROL VOLTAGE-DEPENDENT ACTIVITY OF ANION CHANNELS IN PLASMA-MEMBRANE OF GUARD-CELLS

THE opening of stomatal pores in the epidermis of plant leaves is caused by an increase in turgor pressure of the guard cells as a result of the accumulation of potassium salts 1,2. Although growth hormones have been shown to affect stomatal opening 3, the transduction pathways by which growth regulators exert their effects on stomatal action are largely unknown. Here we report that auxins can elicit stomatal opening. These phytohormones modulate anion channels 4,5 in the plasma membrane in what may be an initial step in regulated volume increase in guard cells. Our patch-clamp experiments demonstrate that auxins can directly interact with the extracellular face of the channel. As a result, its activation potential is shifted towards the resting potential of the cell to favour transient channel opening.