Abstract
Changes in the kind and level of endogenous gibberellins (GAs) in the shoot and ear of rice (Oryza saliva L. japonica variety, cultivar Nihonbare) through its life cycle were investigated. Gibberellin A19 (GA19) was the major GA, and GA1, GA20, GA29 and GA53 were minor GAs in the shoot of rice. Besides these 13-hydroxylated (13-OH) GAs, two non-13-hydroxylated (13-H) GAs, namely GA4 and GA34, were identified in the shoot (containing the ear) collected at the heading stage.
Further studies on the distribution and changes in the level of GAs in reproductive organs revealed that GA4 was highly concentrated in anthers collected just before anthesis, but was not detected in immature seeds collected about a week after anthesis. These results suggest that 13-H GAs may be biosynthesized in specific organs at a specific stage of the life cycle, and that they may be concerned with the regulation of reproductive growth, while vegetative growth is regulated by 13-OH GAs, probably GA1.
