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Bruce W. Wood

stigmatic surfaces and affect pollen germination and subsequent fertilization. Simple nonpigmented flavonoids play a critical role in pollen germination and germ tube growth of several nonwoody dicot species ( Forbes et al., 2014 ; Taylor and Grotewold

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Shengrui Yao

studies regarding pollen amount and pollen germination from China ( Guo and Shan, 2010 ; Han et al., 2008 ; Liu and Peng, 1992 ), but no such studies in the United States. Phenology provides basic information about a fruit species introduction and is

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Patrick J. Conner

, degree of accuracy desired, and the purposes of the test. Typically, germination media is contained within a hanging drop or well, the media is solidified with agar or gel, or the pollen is germinated on a membrane support. Pollen germination media must

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Keith Yoder, Rongcai Yuan, Leon Combs, Ross Byers, Jim McFerson, and Tory Schmidt

germination, pollen tube growth, fertilization and fruit set, and optimum timing for application ( Fallahi and Willemsen, 2002 ; Greene, 2002 ). Several reports have documented that temperature is the most important factor affecting pollen germination and

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M.R. Pooler and R. Scorza

Pollen from the doubled haploid peach [Prunus persica (L.) Batsch] `Hall-D' was irradiated with 0, 290, 530, 820, 1000, 5000, or 9000 Gray (Gy) of gamma radiation, 113 μW·cm-2 of ultraviolet (UV) radiation, or exposed to 100 °C for 2 h. In vitro pollen germination percentages were recorded and pollen was used to pollinate more than 10,000 emasculated or male-sterile peach flowers. Although pollen germination in vitro was stimulated by <1000 Gy of gamma irradiation, seed set following pollination was greatly reduced in all treatments. These results suggest that low levels of irradiation are sufficient to render pollen infertile while still maintaining germination capacity. Such results may be useful for pollination-induced parthenogenetic egg division for the production of maternally derived haploids and for the production of interspecific hybrids.

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Kristina F. Connor, Sharon Sowa, and Robert D. Borchert

A pollen grain undergoes a series of biochemical changes during germination. The technique of cylindrical internal reflectance FTIR was used to examine spectral frequencies associated with respiration, lipid and protein structure, polysaccharide content, and phosphate-containing metabolizes in pollen from pecan, blue spruce, cattail, and pine. Samples of both pollen and germination medium were analyzed at timed intervals. A microscopic evaluation of percent germination was also made at each sampling time. Preliminary analyses indicate that changes in respiration occur as evidenced by the presence of gaseous CO2, and that quantitative changes in lipid and protein occur. FTIR spectroscopy provides a noninvasive method to directly and quantitatively measure metabolic changes associated with pollen germination.

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I.E. Yates and Darrell Sparks

Detached anthers and pollen of pecan [Carya illinoinensis (Wangenh.) C. Koch] were exposed to a range of relative humidities (RH) and/or temperatures to assess the interaction of these environmental factors on pollen dispersal and germination. Dehiscence of anthers was evaluated at selected time intervals following exposure to ≈56%, 33%, 64%, and 97% RH at 10, 21, 27, and 33C in a factorial experiment. Pollen release increased as RH decreased and temperature increased for detached anthers under laboratory conditions and for attached anthers under field conditions. Inhibition of anther dehiscence by high RH could be overcome or minimized with high temperatures and inhibition by low temperatures, in most cases, with low RH. Temperature effects on specific phases in the pollen germination process were evaluated in a sequence of experiments. First, pollen rehydration temperature was varied (3, 15, 29, 33, and 42C) and incubation temperature during tube development kept constant at 25C. After 2 hours of rehydration, tube formation was maximized at 15C and tube length at 29C. Second, all pollen was rehydrated at a constant temperature (25C) and the incubation temperature during tube development varied (3, 15, 29, 33, and 42C). The temperature for maximum tube formation (15C) was different from that for maximum tube length (33C). Morphology of pollen tubes was normal under all rehydration conditions; but, during incubation for pollen tube development, tubes did not develop at 3C and developed abnormally at 42C. The adverse effect on tube development at 3C, but not at 42C, could be reversed by transferring pollen to 25C.

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Madhu Aneja, Thomas Gianfagna, Edward Ng, and Ignacio Badilla

The causes of poor fruit set of cocoa (Theobroma cacao L.) in the greenhouse were studied by examining factors that may influence pollen germination. Hand pollination of cocoa flowers resulted in 45.8% fruit set when flowers were pollinated within 3 hours of anthesis. Pollen germination did not occur until about 6 hours after pollination. Later pollinations (7 to 9 hours after anthesis) or earlier pollinations (16 to 18 hours before anthesis) did not lead to fruit set. Cocoa pollen did not germinate in vitro unless the excised flowers were incubated for 6 hours at 25C in closed vials. During the incubation period, CO2accumulated to a final concentration of about 85 ml·liter-1 as a result of respiration. Ethylene production was not detectable. Incubation of flowers with a NaOH-saturated wick, to absorb CO2, prevented pollen germination in vitro. Incubation of flowers at 15C also prevented pollen germination in vitro at 25C. Hand pollination of flowers 7 to 9 hours after anthesis or 16 to 18 hours before anthesis using CO2-incubated pollen resulted in about 10% fruit set. Enclosed pollinations in vivo, in which CO2 was allowed to accumulate, resulted in nearly 100% fruit set. The initial failure to set fruit from hand pollinations may result from poor or slow pollen germination. Moreover, CO,-incubated pollen might be used to increase fruit set in cocoa by extending the effective pollination period.

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John D. Abbott, B.D. Bruton, and C.L. Patterson

Four fungicides were evaluated for their effects on in vitro pollen germination of muskmelon (Cucumis melo L.) cultivars TAM-Uvalde and Magnum 45. Cupric hydroxide, mancozeb, and chlorothalonil reduced the percentage of pollen that germinated and rate and length of germ-tube elongation, regardless of cultivar. Benomyl had very little overall effect on pollen germination or germ-tube elongation. With the effective pollination period of ≈ 10 to 14 days in commercial production, each day is critical for maximum crown set. Based on our results. some fungicides may be contributing to reduced fruit set in muskmelon.

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Hazel Y. Wetzstein

Commercial pesticide formulations of triphenyltin hydroxide, benomyl plus triphenyltin hydroxide, and phosalone completely inhibited pollen germination of pecan [Carya illinoensis Wangenh C. Koch] when incorporated in in vitro germination media at one-fourth to one times the recommended rates. Scanning electron microscopic evaluations of spray effects on receptive stigmatic surfaces showed varying degrees of injury, ranging from minor surface wrinkling with triphenyltin hydroxide to severe collapse and degeneration of stigma papillae with phosalone treatments. Controlled pollinations 1 hour after pesticide sprays resulted in an inhibition of pollen germination and tube growth. Water sprays followed by pollination resulted in normal pollen adherence, hydration, and germination. Chemical names used: methyl[1-[(butylamino)carbonyl]-1H-benzimidazol-2-yl]carbamate (benomyl); S-[(6-chloro-2-oxo-3-(2H)-benzoxazolyl)methyl] 0,0-diethyl phosphorodithioate (phosalone).