INDUCTION OF LEAF ABSCISSION IN COTTON IS A COMMON EFFECT OF UREA-TYPE AND ADENINE-TYPE CYTOKININS

Cytokinins of the urea and adenine type induced leaf abscission in young cotton (Gossypium hirsutum) plants in the following order of activity: N-phenyl-N'-1,2,3-thiadiazol-5-ylurea (thidiazuron) >> N-phenyl-N'-(2-chloro-4-pyridyl)urea > isopentenyladenine greater-than-or-equal-to 6-benzyladenine > zeatin = dihydrozeatin > kinetin. It is suggested that ethylene production is implicated in this response because it was stimulated by the compounds in cotton leaf discs with nearly the same effectiveness. Moreover, similar to thidiazuron (JC Suttle [1985] Plant Physiol 78: 272-276), isopentenyladenine-induced defoliation was inhibited by aminoethoxyvinylglycine, and the effect was restored by 1-aminocyclopropane-1-carboxylic acid.