In vitro flowering of Japanese pear and the effect of GA 4+7

Abstract

Flower formation of some Japanese pear cultivars, differing in the extent of apical dominance, was studied in relation to young-leaf removal (removing apical dominance) and in vitro vegetative apex culture. In all cultivars, removal of young leaves and disbudding promoted flowering in the remaining axillary buds on the long shoots as compared with only disbudding. The degree of promotion, however, remained within their flowering capacities, indicating that this capacity is inherent in the bud itself. Explants cultured in vitro formed flowers in the bract axils of their main shoot, regardless of whether they were prepared from the shoot apex or the axillary leaf bud. Occurrence of flowering in the explants was closely related to the flowering capacity characteristic of the cultivar from which they were derived. Flowering occurred predominantly in the explants with a particular range of node number, above or below which it decreased rapidly. The presence of gibberellin GA 4+7 in the medium tended to decrease flowering of explants, but had no effect on their node number.