Effects of decapitation,defoliation and stem girdling on axillary bud development in Brussels sprouts

Decapitation of young Brussels sprout plants (Brassica oleracea L. var. gemmifera) which had just produced axillary buds stimulated the development of the upper axillary buds, but this was partially prevented by application of auxin to the decapitated stem. Removal of leaves also stimulated axillary bud outgrowth, even in the absence of decapitation, but only when some of the leaves were left attached. Removal of leaves from the top half of the stem was very effective in stimulating bud outgrowth, whereas removal of basal leaves was ineffective. Steam-girdling the middle of the stem resulted in enhanced axillary bud growth below the girdle and was more effective in defoliated than in leafy plants. The role of the leaves and stem apex in controlling the movement of nutrients and hormones to axillary buds is discussed.