This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by Aharoni, N. Articles by Richmond, A. E. Search for Related Content PubMed PubMed Citation Articles by Aharoni, N. Articles by Richmond, A. E. Agricola Articles by Aharoni, N. Articles by Richmond, A. E.

Articles

Hormonal Activity in Detached Lettuce Leaves as Affected by Leaf Water Content ¹

^a Volcani Center, Bet Dagan, Israel

The interrelationship between water deficiency and hormonal makeup in plants was investigated in detached leaves of romaine lettuce (Lactuca sativa L. cv. `Hazera Yellow'). Water stress was imposed by desiccating the leaves for several hours in light or darkness at different air temperatures and relative humidity. In the course of desiccation, a rise in abscisic acid content and a decline in gibberellin and cytokinin activity were observed by gas-liquid chromatography, by both the barley endosperm bioassay and radioimmunoassay and by the soybean callus bioassay. Gibberellin activity began to decline in the stressed leaves before the rise in abscisic acid, the rate of this decline being positively correlated with the rate of increase in leaf water saturation deficit. Recovery from water stress was effected by immersing the leaf petioles in water while exposing the blades to high relative humidity. This resulted in a decrease in leaf water saturation deficit, a reduction in abscisic acid content, and an increase in gibberellin and cytokinin activity.

Application of abscisic acid to the leaves caused partial stomatal closure in turgid lettuce leaves, whereas treatment with gibberellic acid and kinetin of such leaves had no effect on the stomatal aperture. In desiccating leaves, however, gibberellic acid and kinetin treatment considerably retarded stomatal closure, thus enhancing the increase in leaf water saturation deficit. These results suggest that the effect of desiccation in changing leaf hormonal make-up, i.e. a rapid increase in abscisic acid and a decrease in both cytokinin and gibberellin activity, is related to a mechanism designed to curtail water loss under conditions inducing water deficiency.

¹ Contribution from the Agricultural Research Organization, Volcani Center, P.O. Box 6, Bet Dagan 50200, Israel. 1976 Series, No. 191-E.