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Mary M. Peet, Daniel H. Willits, and Michael Bartholomew

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 3 experiments, 2 in greenhouses and 1 in the phytotron, comparing pollen characteristics of plants grown at differing night temperatures. In the greenhouse studies, nighttime temperatures were kept below 20°C for either the whole night or just the last half of the night. In the phytrotron studies night temperatures were 18, 22, 24 or 26°C, In both phytotron and greenhouse studies, there was considerable day-to-day variability in pollen characteristics and % germination. The most consistent effect in both types of studies was a decrease in total pollen and an increase in % abnormal pollen at high night temperatures. In the phytotron studies 20°C appeared optimal for both these characteristics.

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Mary M. Peet and Michael Bartholemew

Lycopersicon esculentum Mill. `Laura' plants were grown in the North Carolina State Univ. phytotron at 26C day temperature and 18, 22, 24, or 26C night temperatures to determine the effects of night temperature on pollen characteristics, growth, fruit set, and early fruit growth. Total and percentage normal pollen grains were higher in plants grown at night temperatures of 18 and 22C than at 24 and 26C, but germination was highest in pollen produced at 26C. Seed content was rated higher on the plants grown at 18C night temperatures than in any of the other treatments. Numbers of flowers and fruit on the first cluster were lower in the 26C night treatment than in the other night temperature treatments. Plant height was greatest but total shoot dry mass was lowest in the 22C night temperature treatments. Fruit fresh mass increased with night temperature, reflecting more rapid development, but the experiment was not continued to fruit maturity, so the effect of night temperature on final fruit size and total plant production could not be determined. Night temperatures of 26C reduced fruit number and percentage fruit set only slightly at a day temperature of 26C, even though these temperatures were above optimal for pollen production and seed formation. To separate temperature effects on pollen from direct or developmental effects on female reproductive structures, pollen was collected from plants in the four night temperature treatments and applied to stigmas of a male-sterile cultivar kept at 24-18C minimum temperatures in adjacent greenhouses. In the greenhouse-grown male sterile plants, no consistent effects of night temperature treatment given the pollen could be seen in fruit set, fruit mass, seed content (either on a rating or seed count basis), seedling germination, or seedling dry mass.

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Fachun Guan, Shiping Wang, Rongqin Li, Mu Peng, and Fanjuan Meng

the pollen characteristics of P. mira ? 2) Is there a relationship between pollen morphology variation and altitude? 3) Is there a relationship between genome variation and altitude? Material and Methods Plant materials. In this study, all pollen

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Daiichiro Miyajima

The seed producing system in viola (Viola ×cornuta) was investigated to improve seed yield and to save labor. In a flower five anthers sequentially dehisced; pollen grains were continuously supplied to the anterior petal, which played a significant role in pollination, throughout the flowering period. Evidence from pollen and ovule number suggests that the species is facultative autogamy. Each flower opened more than 10 days was independent of the success in fertilization and kept seed producing ability during the flower longevity period. Pollen grains also maintained viability during the flower longevity period. Pollinators were indispensable for pollination of viola, but pollination in viola was done by a different mechanism from the typical insect-mediated pollination that sticky pollen grains adhere to the exposed stigmas. Pollen grains, accumulated around the entrance of the stigmatic cavity, entered into the cavity by the movement of pollinators. Although the visitation of pollinators was occasional, solitary bees primarily contributed to the pollination of viola. On the other hand, germination of pollen grains on the stigmatic surface was under 50%. Seed set was much lower than the germination percentage of pollen grains. A viola flower had the ability for additional pollinations and fertilization for some days after the fertilization success in some ovules in the flower. This characteristic suggested that repeated pollination is effective to increase the number of mature seeds in a capsule.

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Md. Mizanur Rahim Khan, Mst. Hasnunnahar, and S. Isshiki

room for 2 weeks before the plants were transferred to a glasshouse. Identification and characterization of amphidiploids. The number of chromosomes in the root tip cells, size of the stomatal guard cells, and pollen characteristics of F 1 and

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Michael Bartholomew and Mary M. Peet

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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Lihong Hao, Hui Ma, Jaime A. Teixeira da Silva, and XiaoNan Yu

. The P × E value represents the size of pollen grains, whereas P/E represents pollen shape. If P/E > 2, it is perprolate, and if 1.14 < P/E < 2, it is subprolate ( Wang and Wang, 1983 ). Pollen characteristics were observed in equatorial view as well as

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Young-Sik Park, Jae-Yun Heo, and Sun-Bai Bang

.C. Park, S.M. 2005a Growth and fruit characteristics of Vitis amurensis Rupr. collected in Gangwondo Hanguk Yakyong Changmul Hakhoe Chi 13 6 226 233 Park, Y.S. Kim, I.J. Jeong, B.C. Heo, J.Y. Park, S.M. 2005b Pollen characteristics of flower type and

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Luiz A. Biasi and Patrick J. Conner

pollen characteristics of 11 cultivars in the main and secondary flowering period. Similar results were found for ‘Noble’ and ‘Doreen’ in North Carolina where the number of flowers per cluster was 128 and 84, respectively ( Goldy, 1988 ). In the secondary

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Craig E. Kallsen and Dan E. Parfitt

flowering period that is highly coincident with ‘Gumdrop’ receptivity during both low chill and “normal” chilling years. It is the only male cultivar with good pollen characteristics that flowers as early in the season as ‘Gumdrop’. Additional details are