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The effects of ammonium nitrate (AMN) on the penetration of Gibberellin A3 (GA3) into berries of `Kyoho' (Vitis labruscana Bailey) grape during berry development were studied. Treatment solutions of GA3 (100 ng·μL-1) and GA3 + AMN (20 millimolar concentration) were applied to the surface of grape berries under field conditions. The amount of GA3 penetrated was assayed using dwarf rice (Oryza sativa L., cv. Tan-ginbozu). At full bloom, the addition of AMN significantly enhanced GA3 penetration 24, 48 ad 72 hours after application by 13%, 16% and 21% of the applied GA3, respectively, representing a 1.7- to 2.4-fold increase over GA3 alone. At 4 weeks after full bloom (WAFB) at 24 hours after application, 20% of the applied GA3 penetrated in the presence of AMN compared to 15% in the absence of AMN. From varaison (7 WAFB) to maturity (10 WAFB), GA3 penetration decreased, from 6% to 2%, respectively, in the presence of AMN, and from 3% to 1% in the absence of AMN. The addition of AMN to the GA3 solution increased GA3 penetration relative to GA3 alone at all berry developmental stages. On the other hand, Cuticular wax density on the berry surface at 4 WAFB was 1.10 μg·mm-2, 5.8-fold greater than at full bloom (0.19 μg·mm-2). The thickness of the epidermal tissue doubled during the first 2 WAFB, but was maintained almost constant over the next 6 weeks. GA3 penetration was more closely related to the cuticular wax levels than the epidermal tissue thickness.
Abstract
Parthenocarpic fruit development was induced in ‘Montmorency’ sour cherry (Prunus cerasus L.) with AC 94377. The biological activity of AC 94377 was increased significantly by NAA. The development (Stages I, II, III, “June drop”, ripening) of parthenocarpic fruit was similar to that of open pollinated controls except for smaller fruit size. Ovules enlarged during Stage I in AC 94377-induced parthenocarpic fruit, but lacked embryos; all ovules aborted during Stage II or III of fruit development. The primary action of NAA appeared to reduce abscission of AC 94377-treated ovaries with no significant effect on fruit size. Chemical names used: 1-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (6-BA); 1-(3-chlorophthalimido)-cy-clohexanecarboximide (AC 94377); polyoxyethylene sorbitan monooleate (Atlox BI).