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  • Author or Editor: Demetrios G. Voyiatzis x
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Anthesis of an important staminate pistachio (Pistacia vera L.) cultivar (B) in Greece was delayed by foliar paclobutrazol (PBZ) sprays applied in June or July the previous season. A September spray was ineffective. The amount of delay depended on dose (50 to 1000 mg PBZ/liter applied to incipient runoff). Using the same total amount of chemical, one spray was as effective as two sprays 1 month apart. There were no effects on inflorescence fresh weight, pollen production, and pollen germination. Stem elongation was inhibited strongly, but the number of nodes and flower buds per shoot was reduced only slightly. In Expt. 2, two other staminate cultivars (A and C) responded similarly to cultivar B. Treatment effects appeared only during the treatment year, whereas a soil drench was effective for 2 years. PBZ may be able to synchronize the blooming of staminate and distillate pistachio cultivars and result in good fruit set without artificial pollination. Chemical name used: B[(4-chlorophenyl)methyl] -α-(1,1 dimethylethyl)-l H -1,2,4-triazole-l-ethanol (paclobutrazol).

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The role of pollen in abscission of pistillate flowers of Persian walnut (Juglans regia L.) cv. Serr was investigated over a 4-year period by controlled pollinations and pollen counts. Self-pollen, pollen from other walnut selections or cultivars, or dead pollen was applied at high and low doses to pistillate flowers enclosed in pollination bags. Unbagged, open-pollinated flowers and bagged, nonpollinated flowers served as controls. In all cases, presence of pollen significantly increased the probability of pistillate flower abscission (PFA). Dead pollen resulted in as much PFA as live pollen. Counts of pollen grains confirmed that PFA-type flowers had significantly more pollen than normal flowers. In the fourth year `Serr' pollen was applied to unbagged flowers of `Serr' and ten other Persian walnut cultivars, and the amount of PFA on the artificially pollinated flowers was significantly higher than on the open-pollinated flowers, while the control flowers dusted with talc or pine pollen had almost no PFA. These results clearly indicate that excess pollen is involved in pistillate flower abscission in `Serr' walnut and suggests that other cultivars may also be sensitive to pollen load. This phenomenon may have implications in the biology of selfing and evolution.

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