Epidermal abscisic acid [of Vicia faba] as detected by immunofluorescence: Effect of proline

The effect of proline supplied to detached young leaves of Vicia faba L. var. major on the level of epidermal ABA was investigated. After 1 h treatment with 5 min proline, fluorescent isothiocyanate (FITC) labeling of sonicated epidermal peelings indicated a significant increase in the level of endogenous ABA. In a simultaneous experiment on the same material, the effect of 10−7 M ABA on epidermal FITC. fluorescence labeling was also studied. A marked increase in epidermal FITC fluorescence was observed. These results suggest an involvement of proline in the enhancement of ABA bound to the plasma membrane of epidermal cells.