Growth Changes in Disks Cut from Young Leaves ofPhaseolus

Abstract

Disks cut from leaves of different ages were cultured on media with and without added carbohydrate. Relative growth-rates for changes in area of disks were found to be similar to those for intact leaves, and to decline as the age of the parent material increased. Cellular changes occurring concurrently with this decline were followed. Protein per cell was found to increase in disks cultured in the light on sucrose but not in the absence of supplied carbohydrate. This requirement for carbohydrate could not be satisfied by materials produced endogenously in the light, even though under these conditons starch was formed and there were large increases in cell-wall material. Changes in disks and in intact leaves of the same age were broadly similar. The large effects of light and carbohydrate supply are discussed in relation to disk expansion and leaf growth in general.