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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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Donita L. Bryan, Michael A. Arnold, R. Daniel Lineberger, and W. Todd Watson

3 Assistant professor, Department of Forest Science, Texas A&M University, MS 2135, College Station, TX 77843-2135. 1 Graduate student. 2 Professor. This study was included as part of a thesis written in partial fulfillment of the

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Thomas W. Zimmerman and Jacqueline Kowalski

The Sandy Point Orchid (Psychilis macconelliae) is listed as an endangered orchid species by the U.S. Virgin Islands Dept. of Planning and Natural Resources. This orchid grows naturally on the southern dry and wind-swept slopes found on the east-end of St. Croix. It can be found growing among cacti and bromeliads. Due to disturbance to the native habitat from land development, private collectors, and natural disasters, the population has diminished. Tissue culture is being successfully used in a conservation effort for this endangered species. Maturing seed pods were collected and surface disinfested and established in vitro. The medium consisted of one half Murashige & Skoog salts, Nitsch & Nitsch vitamins, 20 g/L sucrose, 2 g/L soy peptone, 5 g/L activated charcoal and 8 g/L agar. Seeds were spread on the medium in 15 × 100-mm petri plates and grown at 25 °C under a 16-h photoperiod. Seed germination occurred within 2 months with the development of protocorms. Leaves and roots developed by 5 months, at which time they were separated and transferred to fresh medium. At 8 months, they were established in a greenhouse and released back into their environment within 12 months. In vitro germination of the Sandy Point Orchid seed is an effective way of conserving this endangered species.

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Pamela D. Adams, Nancy Kokalis-Burelle, and William H. Basinger

This research was performed under a Cooperative Research and Development Agreement (CRADA No. 58-3K95-9-739) with the USDA, ARS and Ajay North America, LLC. Mention of trade names or commercial products in this publication is solely for the

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Sherry L. Hilscher and John E. Preece

Kankakee mallow is an endangered herbaceous perennial that is indigenous to Kankakee County, Illinois. Stock plants were from seeds pretreated in 82°C water prior to greenhouse germination and growth. Nodal explants were disinfested and placed in vitro onto agar-solidified MS medium containing 0, 0.1, 1.0, 5.0, or 10.0 μM BA and 1.0 μM IBA. Axillary shoots grew and elongated best when the medium contained no cytokinin. BA tended to result in a rosette pattern of leaves. Within hours of placing the original explants in vitro and shortly after subsequent transfers were made (even when there was no cutting) a bright pink exudate appeared in the medium. The most vigorous cultures tended to form the most exudate. Microshoots were placed in a high humidity container in vermiculite wetted with water. Rooting was 50% without auxin. Plants were transplanted into pots containing peat-lite medium and successfully acclimatized to the greenhouse.

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Rebecca C.-C. Hsu and Yung-I Lee

investigate the histological and histochemical changes during seed development of C. debile and their relations to the seed germination in vitro. Material and Methods Plant material. Developing capsules of C. debile were collected from a natural population

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Margaret From and Paul E. Read

Platanthera praeclara, commonly called western prairie fringed orchid, is a showy forb native to seven states and one Canadian province. The species had resisted previous attempts at propagation. Small, isolated populations in the sandhills region of western Nebraska are disjunct and visitation by natural pollen vectors appears to be in decline. Modern cultivation practices and other habitat encroachment factors, including urban development, recreational activities, and natural fluctuations in seasonal water availability all have the potential to exert pressure on current populations. Federal and state permits have allowed a limited hand-pollination study to be conducted on federal land. Hand-pollinated plants showed a greater fruit production compared to control plants receiving no human pollination assistance. Germination studies were conducted using aseptic in vitro techniques. The microscopic seeds possess testa that are extremely hard and resistant to liquid absorption, which presents challenges to germination in vitro. These challenges will be discussed. Alternating cold treatments with room temperatures appeared necessary to promote protocorm development after germination. Three media tested produced varying germination responses. Juvenile plants produced through micropropagation can offer propagules for possible future reintroduction efforts of this protected species.

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Khalid M. Elhindi, Yaser Hassan Dewir, Abdul-Wasea Asrar, Eslam Abdel-Salam, Ahmed Sharaf El-Din, and Mohamed Ali

Evaluation of the effect of three growth regulators in the germination of Comparettia falcata seeds under in vitro conditions In Vitro Cell. Dev. Biol. Plant 41 838 843 Pereira, T.S. 1992 Seed germination of Bauhinia forficata Link. (Leguminosae

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Aref A. Abdul-Baki, S. A. Haroon, and R. N. Huettel

Susceptibility of tomato (Lycopersicon esculentum Mill) genotpyes to the root-knot nematode Meloydogyne incognita and to heat stress can be evaluated in a single labor- and time-saving operation using a nondestructive in vitro excised root technique. Seeds are sterilized and germinated for 2 days on 1% water agar. Five-mm root sections are grown at 28 and 35 C for 30 days on Gamborg-B medium with and without nematode inoculum. Evaluation criteria include fresh and dry weight and the appearance of juveniles, adults, gulls, and egg masses. Evidence will be presented on the breakdown of resistance to M. incognita under high temperature stress.

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Todd P. West, Samuel L. DeMarais, and Chiwon W. Lee

.A. Remphrey, W.R. 1993 In vitro germination of three Cypridedium species in relation to time of seed collection, media, and cold treatment Can. J. Bot. 71 879 885 Dirr, M.A. 2009 Manual of woody landscape plants. 6th ed. Stipes Publ., Champaign, IL Dirr, M