Induction of leaf abscission in cotton is a common effect of urea- 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 >/= 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.
Grossmann
K
K
BASF Agricultural Research Centre, 6703 Limburgerhof, Federal Republic of Germany.