Seedling Development in Peach, Prunus persica (L.) Batsch. II. Effects of Plant Growth Regulators and Their Possible Role

Abstract

Treatment of peach embryos from partially stratified seeds with abscisic acid (ABA) inhibited germination and promoted the production of leaf lesions, responses which are typical of testa presence. A period of water stress during germination also promoted lesion production. Neither testas nor ABA stimulated lesions on seedlings from 25°C-stratified seed, but mixtures of ABA and GA*3 were synergistic in promoting lesions; at the same time ABA and GA₃ had opposite effects on germination and stem elongation, and mixtures had intermediate effects. Evidence was obtained for effects attributable to a balance between GA and ABA. Other inhibitors and promotors had no effect on lesions. The results from excision and substitution experiments permit an explanation of the effects of stratification in terms of three events: (a) a decrease in inhibitor activity in the testa; (b) an increase in gibberellin activity in the epicotyl; and (c) diffusion of inhibitor to the epicotyl via the radicle when the seed is returned to warm conditions.