Effect of Indoleacetic Acid in Inhibiting Stem Abscission in Mirabilis jalapa

Abstract

Plants decapitated in the upper portion of the 1st internode when the 2d internode had just started to elongate, and given no additional treatment, showed cessation of growth in the internodes, followed by their abscission after 2 weeks or longer. Preceding abscission, 2 transverse meristems developed. The upper formed across the base of the internode and became the abscission zone. The lower meristem, invariably present when the upper developed. seemed to play no active role in abscission. Little storage starch remained in the cotyledonary nodal region at 2 weeks after decapitation of these plants. Plants similarly decapitated and treated with a 2% indoleacetic acid-lanolin mixture on the cut surface showed continued growth of the internodes, complete disappearance of stored starch, and the entire absence of abscission or of an abscission zone at the bases of the internodes. Untreated, intact plants showed neither abscission nor the formation of an abscission zone at the bases of the internodes.