Characterization of the Kinetin-Induced Water Uptake by Detached Radish Cotyledons

Increase in fresh weight of detached cotyledons of eight cultivars of Raphanus sativus L. was stimulated by kinetin. Dry weight and cell number determinations of the cotyledons revealed that the response was primarily due to water uptake. Inhibition by mannitol, similar rates of 3H2O efflux from kinetin-treated and control cotyledons, and the kinetin-stimulated increases in reducing sugars indicated that the cotyledonary weight gain due to water uptake was dependent upon changes in osmotically active cellular components. The kinetin-induced fresh weight increase was inhibited by 6-methylpurine, streptomycin, chloramphenicol, and cycloheximide. Moreover, the similar patterns of 6-methylpurine and cycloheximide inhibition of the kinetin-induced weight gain and reducing-sugar buildup in detached cotyledons with time showed a close correlation and may be dependent upon RNA and protein synthesis.