Gibberellin (GA), either alone or in combination with para-chlorophenoxyacetic acid (CPA) and b-naphthoxyacetic acid (NOA), induced normal fruit development in a partially sterile raspberry clone at concentrations ranging from 25 to 500 ppm. GA could substitute for pollination in inducing fruit development. Fruit development was more regular when applications were made soon after pollination.
Despite the considerable increases in fruit growth which could be attained, seed and embryo growth were little affected. The numbers of large, seed-containing pyrenes were somewhat reduced by applications at two or eight days after pollination, although not at other times. All the growth substances tended to reduce the width of embryo and seed and to reduce seed size, but these effects were less with later applications.