Polyunsaturated fatty acids modulate stomatal aperture and two distinct K+ channel currents in guard cells.

Regulation of stomatal aperture is critical for both CO2 uptake and water retention by plants. Stomatal opening is produced by osmotic water flow into guard cells, which follows K+ transport across the plasma membrane. We report here that linolenic acid and arachidonic acid, but not several other fatty acids, enhance stomatal opening and inhibit stomatal closing. In patch clamped guard cell protoplasts, linolenic and arachidonic acid rapidly potentiated inward K+ currents and inhibited outward K+ currents, which are carried via distinct K+ channels. These results suggest that certain fatty acids regulate stomatal aperture by modulation of two different K+ channels and may act as second messengers for stimuli that regulate CO2 uptake and water retention by plants.