| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 93 === Summary
Techniques for rapid and easy identification of heat tolerant genotypes in chrysanthemum were studied. The relationship between flowering delay in chrysanthemum and CMT as a measure of heat tolerance, was used to select flowering heat-delay insensitivity in chrysanthemum cultivars and seedlings.
Relative injury (RI) was calculated to assess genotypic differences in CMT for chrysanthemum by measuring the electrical leakage from 25 to 70℃. Sigmoid response curve relationships were apparent between the RI values of all chrysanthemum leaf tissues under different water bath temperatures. A single temperature treatment at 50℃ resulted in RI values near the midpoint of the response curve for summer-grown chrysanthemum cultivars, as compared to 45℃ for winter-grown chrysanthemum cultivars.
Leaves 1-2 to 9-10 from top were taken to measure their RI values, and genotypic differences were greatest in full-expanded leaves 3 to 4 when using CMT test. RI increased with increasing duration from 0 to 30 minutes at 50℃ water bath treatment, and the 30-min treatment exhibited the greatest genotypic differences.
RI value tended to decrease with increasing temperature from 15/13℃ to 35/30℃, summer-grown chrysanthemum grown at temperatures 20 to 35℃ showed heat acclimation. CMT is a useful screening procedure for selecting heat tolerance of chrysanthemums, with 45℃ and 50℃ for 30 minutes for selecting summer-grown and winter-grown chrysanthemum cultivars respectively.
Most cultivars planted grown at 30/25℃ in spring and summer seasons exhibited flowering heat delay, especially for cultivars White Ting-Tzu and Repulse did no flower within 120 days, as compared to those at 25/20 or 20/15℃. But cultivars Remix and Kaa Luoh-Lii exhibited flowering heat delay at 25/20℃ in autumn and winter seasons. Floral development spent long time on phase I, as compared to other phase in chrysanthemum planted in spring and summer season, were delay flowering at experimentation end. Floral development spent longer on phase III in chrysanthemum at daylength from 12.5 to 11.5 hours planted in autumn and winter season.
Planted in spring and summer season, clear linear relationships existed when regressing the RI value on the heat delay of days to flowering in four summer-chrysanthemum cultivars planted in two day/night temperatures between 30/25℃ and 25/20℃, or 30/25℃ and 20/15℃ in phytotron conditions.
Planted in autumn and winter season, linear relationships existed when regressing the RI value on the heat delay of days to flowering in five summer- and six winter-chrysanthemum cultivar planted in two day/night temperatures between 30/25℃ and 25/20℃, or 30/25℃ and 20/15℃ in phytotron conditions.
The CMT of two cultivars Chiu-Yang and Tsai-Yun was measured with leaf and petal discs electrical leakage from 25 to 70℃. Similar sigmoid response curve relationships were apparent between the RI values of two chrysanthemums leaf and petal tissues under different water bath temperatures.
RI values were calculated for open-pollinated seedlings from three chrysanthemum cultivars Tsai-Yun, Rong-Hung and 9721 by measuring leaf electrical leakage. Four groups could be classified according to their RI values in leaves by CMT, including group I ( 1 to 30% RI ), group II ( 31 to 50% RI ), group III ( 51 to 70% RI) and group IV ( 71 to 99% RI ). Seedlings of chrysanthemum cultivars Tsai-Yun and Rong-Hung contained groups II to IV, as compared to groups I to III in cultivar 9721.
Positive linear correlations existed between floral development stage and their associated groups after planting. Faster floral development was coincident with low RI plants.
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