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John Jifon, Kevin Crosby and Daniel Leskovar

Poster Session 46—Temperature Stress Physiology 21 July 2005, 12:00–12:45 p.m. Poster Hall–Ballroom E/F

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Qi Zhang, Kevin Rue and Jeanna Mueller

in Expt. I. Expt. III: Priming effect on seed germination under temperature stress. Seeds of each grass were placed in a 100 × 15-mm petri dish containing 20 mL of 1% agar (Sigma-Aldrich Co.) medium as described in Expt. II and placed in incubators

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Weijie Jiang, Jie Bai, Xueyong Yang, Hongjun Yu and Yanpeng Liu

Thermophilic fruit vegetables, such as tomato, often suffer from suboptimal temperature stress, which is one of the limiting factors in winter vegetable production in China, leading to a decline in production and quality ( Wang et al., 2001

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Jing Mao, Hongliang Xu, Caixia Guo, Jun Tong, Yanfang Dong, Dongyun Xu, Fazhi Chen and Yuan Zhou

As global warming intensifies, the high-temperature stress response of plants has become a key research topic worldwide ( Wahid et al., 2007 ). High-temperature stress often causes a series of morphological, physiochemical, and genetic changes in

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Shiow Y. Wang and Miklos Faust

89 POSTER SESSION 13 Temperature Stress/Cross-Commodity

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Tianna W. Weathington* and DeviPrasad V. Potluri

Axillary bud cultures of sweetpotato Ipomoea batatus L. [cultivars comensal and salyboro] were propagated in vitro. Nodal cultures of these were grown at different temperatures ranging from 10 °C to 30 °C at 5 °C intervals from the time of axillary bud transfer to 10 weeks of growth in a controlled growth chamber. After 10 weeks of growth, morphological and physiological parameters were measured including shoot height, number of nodes and branches, levels of proline, soluble carbohydrate and protein. There was not much difference in the cultures grown at 25 and 30 °C but temperatures lower than 25 °C were inhibitory to both cultivars, though the effects were more pronounced in salyboro than comensal. Salyboro grew slower and exhibited leaf discoloration, weak stems, and poor root growth. Proline levels increased in both cultivars and the increase was higher in shoot than root due to low temperature stress. Soluble carbohydrates and proteins increased in comensal, maintaining the carbohydrate protein ratio, but decreased in salyboro. The results suggest that the cultivar comensal may tolerate cooler temperatures and the cultivar salyboro is susceptible to them.

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Ahmet Korkmaz and Robert J. Dufault

Watermelon [Citrullus lanatus (Thunb) Matsum. & Nakai.] seedlings may be repeatedly exposed to temperatures alternating between almost freezing and optimum soon after field transplanting. `Carnival', `Crimson Sweet', `Millionaire' and `Crimson Trio' watermelon transplants were exposed to cold temperature stress at 2 ± 1 °C in a walk-in cooler and then to 29 ± 5 °C in a greenhouse immediately before field planting to simulate temperature alternations that may occur after field transplanting. Cold-stressed transplants were field planted after all risk of ambient cold stress passed. In 1998, transplants were exposed to 2 °C from 9 hours to 54 hours, and in 1999 from 9 to 81 hours. Early yields of all cultivars, except Carnival, significantly decreased with increasing hours of cold stress in both years. Total yields of `Carnival' decreased linearly in both years with a 10% yield reduction occurring from 14 to 15 hours of cold stress. `Crimson Sweet' yields were reduced in 1999 only, with 16 hours of cold stress reducing yield 10%.

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Jin Jiao, Xing Liu, Juyou Wu, Guohua Xu and Shaoling Zhang

evolutionary history. To verify their functions in pollen, we analyzed the expression pattern in pollens of chinese white pear MAPK genes by quantitative polymerase chain reaction (qPCR) in response to temperature stresses and various hormonal changes. In

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Suping Zhou, Roger Sauve, Tingting Chen, Sara Bhatti and Debrah Long

Poster Session 46—Temperature Stress Physiology 21 July 2005, 12:00–12:45 p.m. Poster Hall–Ballroom E/F

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M. Oren-Shamir and Dela Gal

Changes in temperature during rose flower development, often cause a significant fading of flower color, decreasing its market value. We are studying the effect of transient high temperature stress on red roses (Rosa ×hybrida, `Jaguar'). We have found that a transient temperature stress of 39/18 °C day/night respectively for 3 days, in comparison to the growth temperature of 26/18 °C, caused a significant fading to flower color at a mature bud stage. The plant organ responsible for color fading is the flower bud only. When the stress was applied to the whole plant, not including the flower buds, there was no change on the mature bud color. We have also shown that there are specific flower developmental stages sensitive to the transient increase in temperature. Flower buds at the critical stage of development, that have been exposed to temperature increase have a faded pink-red color when matured. Total anthocyanin levels of faded flowers, due to temperature stress, decreased to ≈50%. In addition, the ratio between the two anthocyanidins composing the red color, cyanidin and pelargonidin, changed dramatically due to the temperature stress: flowers on plants that have not overcome a temperature stress had a ration of 1:1, while those that have faded due to the temperature stress have a ration of 2:1 of pelargonidin to cyanidin, respectively. These findings hint to specific stages of anthocyanin synthesis, that are hypersensitive to increased temperature. We are now in the process of identifying and characterizing these stages.