The Nature of Shoot Dominance in White Yam Tubers (Dioscorea rotundata Poir)

Abstract

The nature of shoot dominance in white yam tubers (Dioscorea rotundata Poir) was studied under ambient conditions in the conventional yam storage barn. Whole tubers sprouted only at the proximal ends (i.e. the morphological bases). The single basal shoot formed per sprouting whole tuber inhibited the formation of lateral shoots along the tuber axis. Separating the basal end by sectioning the tuber into three regions namely "head" (i.e. basal or proximal region), middle region and "tail" (i.e. apical or distal region), appeared to stimulate the formation of lateral shoots on the surfaces of the tuber pieces below the basal region. Separating the basal region from the entire tuber by sectioning appeared to remove the stress under which the lateral buds had existed in the intact tuber. This response indicated a strong "basal dominance" of basal shoots in sprouting intact or whole yam tubers. The physiology of shoot dominance in whole yam tubers could be described as "basal dominance" rather than "apical dominance", since in sprouting intact or whole tuber it is the basal shoot (i.e. shoot of the morphological base or proximal end) that inhibits the development of lateral shoots along the tuber axis.