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  • Author or Editor: Donald L. Sowers x
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`Redhaven' peach [Prunus persica (L.) Batsch] trees were shaded to five light levels [100%, 45%, 23%, 17%, and 9% photosynthetic photon flux (PPF)] for four different periods. Net photosynthesis (Pn), measured under the various shade levels, increased nonlinearly with increasing percent PPF. After 18 days of shading, specific leaf weight (SLW) was positively and linearly related to percent PPF. After shade removal, Pn and SLW returned to control levels in 26 and 4 days, respectively. Flower density was positively related to percent PPF when trees were shaded from 16 June to 4 July or 4-31 July, but not from 31 July to 30 Sept. of the previous year.

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The relationship between peach [Prunus persica (L.) Batsch] fruit position and fruit weight (FW) was studied in experiments involving thinned vs. nonthinned fruiting shoots, shoots with and without axillary shoots, and trees with varying crop densities (CDs). FW was not consistently related to position on the shoot, and the influence of fruit position varied depending on the presence of axillary shoots on the fruiting shoot. FW was best related to fruiting shoot length and total shoot length per fruit (1-year-old plus current-season wood). Mean FW was also influenced by the number of fruit per shoot × CD interaction, a result indicating that FW depends on photosynthate from leaves in the immediate vicinity of the fruit as well as photosynthate from more distant parts of the tree.

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Abstract

Various chemicals were applied to whole-tree, quarter-tree, or single-limb units to determine their efficacy for delaying apple (Malus domestica Borkh.) fruit abscission. NAA and the herbicides fenoprop, dicamba, triclopyr, lontrel, fluroxypyr, and chloroxuron delayed fruit abscission. Benzoic acid, calcium acetate; the growth regulators lactidichlor ethyl, mefluidide, BA, GA4+7, and chlormequat; and the herbicides pronamide, pendimethalin, chloramben, and DCPA did not delay fruit abscission. Chemical names used: benzoic acid,3,6-dichloro-2-methoxy,2-ethoxy, 1-methyl,2-oxoethylester (lactidichlor ethyl); 1-naphthaleneacetic acid (NAA); N-(phenylmethyl)-1H-purin-6-amine (BA); gibberellin (GA4+7); N-[2,4-dimethyl-5-[[(trifluoromethyl)sulfonyl]amino] phenyl]acetamide (mefluidide); 3,5-dichloro(N-1,1-dimethyl-2-propynyl)benzamide (pronamide); N-(1-ethylpropyl)-3,4-dimethyl-2,6-dinitrobenzenamine (pendimethalin); 3,6-dichloropicolinic acid (lontrel); 3-amino-2,5-dichlorobenzoic acid (chloramben); 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat); 4-amino-3,5-dichloro-6-fluoro-2-pyridinyl oxyacetic acid (fluroxypyr); butanedioic acid mono 2,2-dimethylhydrazide)4-chlorophenyl)methyl]-(1,1-dimethylethyl)-1-H-1,2,4,triazol-1-ethanol (paclobutrazol); N'-[4-(4-chlorophenoxy)phenyl]-N,N-dimethylurea (chloroxuron); dimethyl tetrachloroterephthalate (DCPA); 3,6-dichloro-2-methoxybenzoic acid (dicamba); 2-(2,4,5-trichlorophenoxy) propanoic acid (fenoprop).

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Five apple (Malus domestica Borkh.) cultivars were treated with dicamba at concentrations of 0 to 200 mg·liter-1 during 3 years. Although the response varied with cultivar, dose, and year, dicamba always delayed fruit abscission. At similar concentrations, dicamba usually reduced fruit drop more than NAA, but less than fenoprop. Dicamba at 10 mg·liter-1 effectively delayed drop of `Delicious', whereas 20 to 30 mg·liter-1 was required for `Red Yorking', `Rome', `Winesap', and `Stayman'. Dicamba did not influence flesh firmness, soluble solids content, water core, or starch content at harvest or after storage. Chemical names used: naphthaleneacetic acid (NAA); 2-(2,4,5-trichlorophenoxy)propionic acid (fenoprop); 3,6dichloro-2-methoxybenzoic acid (dicamba).

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