Occurrence of gibberellin a(3) in parthenocarpic apple fruit.

The gibberellins 'have ibeen established as effective fruit setting agents (5). In the apple, where auxins are generallly inactive, the gi'bberellins induce parthenocarpy and sustain fruit growth to maturity (2,6, 10). This pronounced fruit-setting activity and the estafblished observation that asymmetric growtth of apple fruit is related to incomplete seed development, -has encouraged investigations on the rela.tionship of endogenous seed gi!bberellins to fruit-set and growth. Gibbetrel'lin-like activity 'has been demonstrated in endosperm (11) and GA4 and GA7 identified in immature apple seed (8). The biosynthesis of gibberellins by 'seeds is viewed as a specific role of seeds in fruit-set o.f the apple (7). However, some cultivars of Malus are prone to produce seedless fruit after exposure to 'low temperature during the fruit-setting period. The presence of gibberellinlike substances in such parthenocarpic fruiit is, herein, reported. Immature seedless apple fruits (Malus sylvestris iMill., selection New Jersey 12) developing subse-quent to 'a severe 'frost, 4 days after full bloom, were harvested (6-wk post-tbloom), frozen immedi.altely and stored at -300 until used. Frozen fruits (6.9 kg) were immersed in 100 % acetone (7.6 liters), then each fruit was halved to check for seedlessness (no seeds were found), homogenized in acetone and extracted twice 'by stirring tinder nitrogen for 24 hours at 2°. The filltrates were comibined and concentrated to an aqtueoous solultion (3.5 liters, pH of 2.8) in vacuo. The pH of the filtrate was increased to 6.0 with 10 % KOH (13) and centriffuged to remove proteins and other insoluble substances. The supernate was washed with n-hexane and adjusted to pH 2.0, stiirred for 2 hours a'fter a'ddition of 70 g of activated charcoal and filtered. The charcoal was washed several times with distilled water and eluted with acetone. The eluate (acetone) was ev-aporated 'to dryness, the residue (2.62 g) stus-