| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 96 === Eight Chinese kale (Brassica oleracea L. var. alboglabra) varieties (‘Yellow-flowered kai-lan’, ‘Kai-lan Flower’, ‘Kai-lan Tai’, ‘White-flowered Big- stemmed kai-lan’, one F1 variety, ‘Black-leaf kai-lan’, ‘Si-lo kai-lan’ and ‘White -gelin’) were used in the study, including ones for tender leaf use or for fleshy flower stalks. All varieties were grown in a phytotron with room temperature of 25/20℃ (day/night) for four weeks before being treated for 3 days of one of the three stresses, namely, flooding at room temperature (25/20℃), high temperature (35/30℃) only and flooding at 35/30℃ at National Taiwan University. Plants kept at 25/20℃ served as the control. All plants were given recovery at room temperature (25/20℃) for three days after stress treatment. Plants were sampled both after 3 days of stress and after three days of recovery to investigate the physiological responses including plant growth score, fresh and dry weight, relative water content, proline content, chlorophyll content, malondialdehyde (MDA) content and electrolyte leakage in order to evaluate varietal difference and the relevance of these physiological parameters to be used as a selection indicator in breeding program. The results showed that parameters of fresh and dry weight, relative water content and electrolyte leakage varied little or without consistent pattern and difficult to be as an indicator to distinguish varieties different in tolerance. Physiological parameters of chlorophyll content and MDA content showed similar variation among different varieties and proline content was the only parameter showed dramatic variation among varieties in response to stress treatments. Accordingly, proline was used as a criterion for further screening in the field. Variety ‘Si-lo kai-lan’ responded with little variation of various physiological parameters showing good tolerance to flooding at room temperature (25/20℃), whereas cv. ‘Kai-lan Flower’ had prominent changes showing sensitivity. In response to three days of high temperature (35/30℃) and the following 3 days of recovery, cv. ‘Black-leaf kai-lan’ and the F1 variety showed better heat tolerance than other varieties in terms of leaf cell membrane thermostability and small change of other physiological parameters. The F1 variety and ‘Si-lo kai-lan’ each with little variation of some physiological parameters showed the best tolerance to flooding at high temperature (35/30℃), while ‘Kai-lan Tai’ was sensitive to the stress. Based on all examined responses of eight Chinese kale varieties, cvs ‘Kai-lan Flower’ and ‘Kai-lan Tai’ grown for their fleshy flower stalks and suited in cool season showed sensitivity to heat and flooding, whereas cvs. ‘Black-leaf kai-lan’, ‘Si-lo kai-lan’ and the F1 variety all grown for their tender leaves year round showed better tolerance. All 8 varieties were grown at temperature of 25/20℃ (D/N) in a phytotron for four weeks before being sampled to test their membrane thermostability and the leaf discs were put in water bath of 50℃ for 10 minutes. The electrolyte leakage was measured by electrolyte conductivity meter. The relative injury (RI) of cv. ‘White-flower Big-stemmed kai-lan’ , cv.‘Si-lo kai-lan’, the F1 variety, cv. ‘Black-leaf kai-lan’ and cv. ‘Kai-lan Flower’ ranged between 41.8 % and 52.4 % indicating higher cell membrane thermostability. Varieties ‘Yellow-Flower kai-lan’ and ‘Kai-lan Tai’ followed with RI of 74.4 % and 76.0 %, respectively. Relative injury of ‘White-gelin’ had the highest RI of 88.31 % and the lowest cell membrane thermostability. The heat acclimation of 35/30℃ for 24 hours significantly reduced relative injury of all varieties, i.e. ‘White-gelin’ to 45.3 %, ‘Kai-lan Tai’ to 34.7 %, ‘Black-leaf kai-lan’ and F1 variety down to 13.9 % and 9.7 %, respectively. Although heat acclimation could improve heat tolerance of Chinese kale, same order of varieties in relative tolerance remained. Field experiment with 47 varieties was carried out at Agricultural Research Institute, all plants were waterlogged for 3 days after 3 weeks of transplanting to the farm and then drained to recover for 6 days. Prolin content of each variety was evaluated after flooding and plant growth score and survival rate were recorded after recovery. The results showed that varieties with lower survival rate had leaf proline content much increased and the tolerant varieties had prolin increase in small magnitude. The leaf proline content and plant growth score or survival rate was negatively correlated. The effect of seed immersion for four days on germination was studied on 8 varieties. Seeds were immersed at room temperature of 25℃ or at high temperature (35℃) or just pretreated at 35℃ for four days before germination at room temperature. Seeds viability was decreased after immersion treatment. The F1 variety still had high germination rate after three stress treatments in accord with its plant tolerance to high temperature and flooding.
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