Effects of Sucrose on Rooting and Senescence in DetachedRaphanus sativusL. Cotyledons

Abstract

Application of 0.5–4.0 per cent sucrose to excised radish cotyledons incubated in the light suppressed the formation of roots, enhanced the rate of yellowing, and altered the location of chlorophyll loss from the margin of the lamina to the petiolar region in most of the cotyledons. These effects were not produced when osmotica such as mannitol or polyethylene glycol were used. A few cotyledons were able to root in the presence of sucrose and these showed enhanced yellowing at the margin. The number of such cotyledons increased when they were incubated in water for the period during which primordium initiation begins, before transfer to sucrose. However, the pattern of yellowing in the presence of sucrose was not affected by the repeated removal of the region of primordium development, suggesting that the pattern of senescence is not controlled by the formation of root primordia. The results are discussed in relation to the effects of light and possible accumulation of carbohydrate on senescence and root formation in excised tissues.