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

AUTOR(ES)

Aharoni, Nehemia

RESUMO

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.

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