Storage Organ Development in Radish (Raphanus sativus L.). 1. A Comparision of Development in Seedlings and Rooted Cuttings of Two Contrasting Varieties

Development was compared in two contrasting varieties of radish grown in nutrient solution. Differences in shape of the long, tapering radish of Long White Icicle and the smaller, round Cherry Belle were associated with differences in the growth of the upper part of the tap root. Thickening was the result of , cambial activity and transverse scctions through the upper root showed differences in both cell number and a l l size. Long White Icicle contained more cells in the secondary xylem and phloem/secondary cortex than Cherry Belle, and the non-lignified xylem parenchyma cells were also larger in Icicle. The upper part of the tap root also elongated in Icicle but not in Cherry Belle, and this was entirely due to an increase in cell number in the longitudinal plane. Removing the distal part of the root system had little effect on storage organ size unless most of the root system was removed. Adventitious roots on seedling and shoot-tip cuttings of both varieties were capable of thickening and the single root developing on shoot-tip cuttings of Cherry Belle achieved a diameter greater than that of the radicle of the intact plant. Rooted cotyledons of Cherry Belle cxrasionally produced small storage organs.