An Interaction between the Effects of Kinetin and Gibberellin in Retarding Leaf Senescence

The relation hetween the effects of kinetin and gibberellin on retardation of leaf senescence was studied. Leaf discs were incubated for five days in several hormone concentrations, the chlorophyll was extracted and its amount estimated spectrophotometrically. Investigation of leaves from actively growing plants of Taraxacum megalorrhizon and Tropaeolum majus showed that an interaction existed between the effect of both hormones. Leaf age, light intensity and day length had a marked effect on the degree of response to the hormonal treatments, hut the change in response effected by these conditions remained similar for both hormones. Possible interpretations of the interaction observed between the effects of kinetin and gibberellin are discussed.