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of artificial pollination and pollen storage protocols. Germination tests have generally been considered to be the best in vitro indicator of pollen usefulness ( Galleta, 1983 ). The in vitro germination test assesses the viability of a pollen sample

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Avocado pollen was germinated in vitro without recourse to germination on the style. The technique employed involved inclusion of pollen grains in liquid medium of 15% sucrose and minerals and application of 1 or 2 drops on 1% agar plus 15% sucrose and minerals. No germination was obtained on agar plus sucrose without placement of pollen in liquid first. Of the cultivars tested, ‘Ettinger’ and ‘Nabal’ pollen germinated best, and ‘Fuerte’ was the poorest. The optimum temperature for germination was 25° to 27°C. Addition of Ca to the liquid proved beneficial.

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Abstract

In vitro germination of freshly collected pollen from pecan [Carya illinoensis (Wangenh.) C. Koch) was examined following exposure to relative humidities (RH) of ≈5%, 50%, and 97% and temperatures of 25, 35, and 45C in a factorial experiment. Maximum germination percentage occurred as RH increased and temperature decreased. Pecan pollen stored for nearly 2 years at −80C and −196C, but not −10C, retained germination capacity equal to freshly collected pollen if stored pollen was given a period of controlled rehydration before in vitro assay for pollen tube formation. Differences in germination of pollen stored at −10C and −196C were substantiated with the fluorochromatic test procedure as well as light microscopy. Pollen removed from storage at −196C and left at ambient laboratory conditions for 59 days retained the capacity for in vitro germination.

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Abstract

The morphology of pecan [Carya illinoensis (Wangenh C. Koch)] pollen from 4 cultivars was examined using light and scanning electron microscopy. Pollen was triporate, paraisopolar and suboblate, with a tectate and microechinate surface. The exine was thickened around pores. Pollen from the 4 cultivars was indistinguishable. Pollen germinated in vitro after 1 hr. Pollen tubes grew from 1 or 2 pores, with one germ tube becoming dominant. Pollen germination decreased dramatically after anther dehiscence. Less than 1% of the pollen germinated 5 days after collection.

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Abstract

Pistachio (Pistacia vera L.) pollen was examined for capacity to germinate in vitro 2 days after anthesis and at intervals of time after storage at ambient laboratory conditions or at − 20°C. In 1986, fresh pollen of each of four clones examined had high germination percentages on a range of sucrose and agar concentrations. After 1 week at room temperature, germination percentages were < 6%. However, when the same week-old pollen was treated to effect gradual hydration at high humidity prior to being placed on the germination medium, germination increased to > 80% for ‘Peters’ pollen and 10.4% to 63.8% for the three other clones. In 1987, similar results were obtained for ‘Peters’ pollen, where pollen hydrated at high humidity had germination rates at least 50% that of fresh pollen when stored up to 18 days at ambient laboratory temperature and humidity. Pollen stored at −20° showed more exacting in vitro germination requirements than fresh pollen, particularly as time in storage increased. ‘Peters’ pollen retained germination levels comparable to fresh pollen after 4 months at −20°, but, by 12 months, germination percentages had fallen sharply.

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Abstract

Conditions for in vitro germination of jojoba [Simmondsia chinensis (Link) Schneider] pollen were optimized in order to study the influence of storage temperature on viability. A medium consisting of 300 mg·liter−1 CaCl2·2H2O, 100 mg·liter−1 KNO3, 10 mg·liter−1 H3BO3, 20% sucrose, and 4% to 5% Difco Bacto-agar was optimal for germinating both fresh and stored pollen. Pollen germinated readily in media with a pH range of 4 to 8. The optimum incubation temperature range for pollen germination was 25° to 30°C. When stored at room temperature (22° to 25°), the initial pollen viability was decreased to 50% in 3 weeks and to 0% after 10 weeks, as determined by in vitro germination. Pollen stored at 4° maintained its initial viability for 10 weeks, followed by a gradual decrease in germination to 70% in 17 weeks and 0% after 22 weeks. Pollen stored at −196° in liquid nitrogen for 2 years retained a germination percentage as high as that of fresh pollen. The eryogenieally stored pollen, when used in controlled pollinations, produced normal fruit set comparable to that with fresh pollen.

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The sporadic nature of inflorescence production and flower protogyny in caladium (Caladium ×hortulanum Birdsey) makes it desirable to store pollen and to rapidly assess its viability for cross-pollinations in breeding programs. This study was conducted to develop a procedure to determine caladium pollen viability and to use that procedure to evaluate the effect of short-term storage conditions on pollen viability. The sucrose level in the culture medium was found to have a significant impact on the in vitro germination of caladium pollen; a concentration of 6.8% was determined to be optimal for pollen germination. Caladium pollen lost viability within 1 day under room (24 °C) or freezing (-20 °C) temperatures, but could be stored at 4 °C for 2 to 4 days. Pollen stored at 4 °C produced successful pollinations. Data obtained from large-scale greenhouse pollinations supported use of this in vitro germination assay as a convenient way to evaluate caladium pollen viability (and fertility).

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Previous greenhouse studies in Raleigh have shown that nighttime cooling increases tomato fruit weights from 11% to 53%, depending on planting dates. The physiological mechanism was unclear, except that temperatures during fruitset were most critical We report here on a phytotron experiment comparing pollen characteristics and in vitro pollen germination of plants grown at night temperatures of 18, 22,24 or 26°C in a 12-hour photoperiod with 26°C day temperature in all treatments. There was considerable variability between sampling dates in pollen characteristics and % germination. The most consistent and significant effects were a decrease in total pollen and an increase in % abnormal pollen at high night temperatures. Number of seed present in the fruit also decreased with increasing night temperatures, indicating that the changes in pollen characteristics adversely affected seedset. Night temperatures of 22C appeared optimal for many of the pollen and growth characteristics measured, but fruit developed most rapidly at the higher night temperatures.

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In almond [Prunis dulcis (Mill.) D.A. Webb.], fungicide sprays are required to prevent blossom blight, which can infect open flowers. Numerous studies have reported detrimental effects of agrochemical sprays on pollination, fruit set, and yield in tree fruit crops. However, effects of fungicides on pollen germination and growth in almond are little known, particularly those from recently developed active ingredients. In this study we evaluated the effects of commercial formulations of 10 fungicides on pollen germination and tube growth in almond using in vitro assays. Assays conducted at 1/100 recommended field rates (RFR) were effective in delineating differences in almond pollen sensitivity to different fungicides. Captan and azoxystrobin were the most inhibitory, with germination percentages of less than 1% of the no-fungicide control. Germination was not significantly affected by propiconazole and benomyl. Intermediate inhibitory effects on pollen germination were observed with ziram, cyprodinil, maneb, thiophanate-methyl, iprodione, and myclobutanil. In contrast to germination, tube growth was less affected by the presence of fungicide. In pollen that germinated, tube elongation was the same as in controls in five of 10 of the fungicides evaluated. Nonetheless, azoxystrobin and captan reduced tube elongation by ≈90%. Some fungicide treatments also influenced tube morphology. In the absence of field evaluation studies, in vitro germination data may provide insight on how specific chemicals may impact pollination processes and further guide in vivo studies, particularly in the case of new chemical formulations.

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masculinized female hemp genotypes. Materials and Methods In vitro pollen germination was evaluated for five masculinized female hemp genotypes, Abacus, Cherry Wine, Mountain Mango, Wife, and Youngsim10, and two male hemp genotypes, Kentucky Sunshine and

Open Access