THE INFLUENCE OF SURFACTANTS ON TRANSPIRATION OF STRAWBERRY LEAVES

Surfactants introduced into strawberry (Fragaria grandiflora Duch. cv. Redgauntlet) leaves in doses of 5.5 x 10(-4) - 5.5 x 10(-2) mumol per leaf blade decreased the transpiration rate of treated leaves regardl ess of the electrical charge brought to the membranes. A 5.5 x 10(-2) mumol dose of surfactants applied during constant illumination caused almost the same decrease in transpiration as a dose of 7.5 x 10(-4) mu mol of abscisic acid. Surfactants also accelerated the decrease in tra nspiration in plants grown in the dark, and there was a consistent rat e of solute efflux from guard cells. Fusicoccin applied to plants unde r the influence of surfactants or abscisic acid caused a sustained inc rease in the transpiration rate. Mannitol and sucrose caused a tempora ry increase in transpiration rate. KCl increased transpiration when ap plied after abscisic acid but decreased transpiration when applied aft er surfactants. These observations suggest that surfactants and abscis ic acid influence the guard cell membrane in different ways and that t he electrical charge introduced on the plasmalemma surface is not esse ntial in the regulation of stomatal aperture.