The levels of endogenous gibberellin A1 and A19 (GA1 and GA19) and abscisic acid (ABA) in three rice (Oryza sativa L.) cultivars, Nihonbare (normal), Tan-ginbozu (semid-warf) and Tong-il (semi-dwarf), were measured at various stages of internode elongation and ear development. GA19 was the main GA in Nihonbare and Tong-il throughout the life cycle but was not detected in Tan-ginbozu. The levels of GA1 in the ears of all three cultivars were low and reached their maxima after anthesis. Similarly, the ears of all three cultivars contained high ABA levels which peaked after anthesis. Shoots contained low quantities of ABA throughout the life cycle. The roles of GAs and ABA are discussed with respect to physiological phenomena, such as internode elongation, ear development and dwarfism.
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Suzuki et al. (1981) studied this question.