Gibberellin-like Substances in Apple Seeds and Fruit Flesh1

Gibberellin (GA)-like substances in extracts of immature apple ( Malus domestica Borkh.) seeds and fruits were partially purified by paper and column chromatography. Following silicic acid column chromatography, two zones of activity (S-I and S-II) were observed in seed extracts, occurring at the approximate elution volumes of GA 4/7 and GA 5/6 respectively. On thin layer chromatograms, most of the biological activity of S-I occurred at the Rf of GA 4/7 , although an additional less polar GA-like component appeared to be present; that of S-II occurred at the Rf of GA 3 . Both S-I and S-II were active in all 5 bioassays used. Levels of both components were at a maximum in early July, shortly after June drop. Bioassay of extracts prepared at this time indicated that over 95% of the activity occurred in the endosperm. Extracts of fruit flesh contained two GA-like components, both more polar than GA 4/7 . Activity per unit fresh weight was approximately 3000 fold higher in seeds than in fruit tissue. The possible roles of these compounds in fruit development and flowering are discussed.