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Patrick J. Conner

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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Nina Devrnja, Jelena Milojević, Ljiljana Tubić, Snežana Zdravković-Korać, Aleksandar Cingel, and Dušica Ćalić

; Wodehouse, 1935 ). In vitro pollen germination and pollen tube growth are greatly influenced by different factors. For example, addition of sucrose to the germination medium improved in vitro pollen germination frequency and tube growth by preventing tube

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Bruce W. Wood

− )] known to be requisite for a degree of in vitro pollen grain germination and subsequent germ tube growth. Findings from other species are suggestive that other important growth promoting or inhibiting chemicals, such as flavonols, are also present under

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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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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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Jessica DiMatteo, Lauren Kurtz, and Jessica D. Lubell-Brand

output from genetically male plants. We have observed that some female hemp strains make better pollen parents than others following masculinization with STS. The objective of this study was to evaluate differences in germination of pollen from five

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Vito S. Polito, Steven A. Weinbaum, and Tom T. Muraoka

Experiments were conducted to determine if differential responses of walnut pollen germination to temperature, previously observed to occur among genotypes, were genetically fixed or expressions of phenotypic plasticity representing adaptive responses to temperatures experienced during pollen development. Individual branches of a single walnut (Juglans regia L. cv. Serr) tree were warmed above ambient conditions during the final stages of pollen differentiation by directing a stream of moist, heated air into polyethylene enclosures, each containing an individual branch unit. Pollen was collected at staminate anthesis and incubated in germination medium on a temperature gradient apparatus. Model curves fitted to the in vitro pollen germination data were used to determine optimum germination temperatures. We found adaptive responses of pollen germination to temperatures experienced during pollen development. The optimum temperature for in vitro germination for pollen from branches maintained under ambient conditions was lower than that of pollen from branches with elevated temperature, and optimum germination temperature increased as a log function of integrated daily temperature (degree-days) experienced during pollen development.

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Zhanao Deng and Brent K. Harbaugh

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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Vikramjit S. Bajwa* and Curt Rom

Osmotic agents used to prevent apple pollen grain germination were studied in vitro by applying 10 μL of solutions to germinating apple pollen on germinating and growth media. Seven concentrations (0%, 0.25%, 0.5%, 1%, 2%, 5% and 10%) of the solution were prepared for each chemical and the characteristics of pH, EC, and osmotic potential were measured. Apple pollen was dispersed onto the media in petri dishes. Micro drops of solution were then applied to marked areas. Dishes were then placed in germination cabinets at 25 °C. Cumulative percentage pollen germination was calculated 4, 8, 12, and 24 h after treatment by microscopic observation. Generally, the cumulative percentage pollen germination decreased asymptotically with increasing chemical concentration. The most effective chemicals for restricting pollen germination and growth were CuSO4 (0.25%), CH3 COOH (0.25%), CaCl2 (10%), K2 S2 O5 (0.25%), Methyl Jasmonate (2%). The effect of these chemicals has also been tested on pistil viability both in vitro and on excised limbs.

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M.R. Pooler and R. Scorza

Research Service (USDA-ARS), Byron, Ga., for cooperative use of peach trees; Peter Seferian, USDA-ARS, Beltsville, Md., for assistance with pollen irradiation; and Lenard Gilreath, USDA-ARS, Kearneysville, W.V., for assistance with pollinations. The cost of