| Summary: | 碩士 === 國立臺灣大學 === 園藝學研究所 === 97 === Heat stress causes a series of morphological, physiological and biochemical changes in potato (Solanum tuberosum L.) plants and results in adverse effect on the tuber production. In this study, the responses of potato to high temperature were monitored by the variation of the cellular membrane thermostability, proline content, chlorophyll fluorescence parameters and chlorophyll meter reading (SPAD values) in leaf. The clonal difference in heat tolerance was evaluated with ‘Kennebec’ as a reference. The relative injury values ranged between 62% and 95.8% with a decreasing tendency along with increasing growth period in ‘Kennebec’ when sampled at 30-52 days after planting from a farmer’s field in Chia-yi. The analyses of cellular membrane thermostability of potatoes at TARI in summer showed that clones with lower relative injury (RI) values had higher tuberization rate. The ‘Kennebec’ failed to produce any tuber and, out of other 27 clones tested only two of 97.1 seed progenies had significantly lower RI value than that of ‘Kennebec’. In 22 clones tested from the fall crop (planted in mid September) of TARI, clone PS3-2 and one clone of 97.1 had RI value significantly lower than that of ‘Kennebec’. The effect of acclimation at 35/30℃(day/night) for 24 hours was revealed by the reduced RI value in both ‘Kennebec’ and LT-7, and among 13 other tested clones, PS-1 and PS-2 were considered more heat tolerant than ‘Kennebec’ for their low RI values. Proline content of four potato varieties increased under 30/25℃ for 7 days , the respective SPAD values taken at 14 days of treatment decreased. At harvest, ‘Kennebec’ had 79% reduction in tuber fresh weight and the clone without tuber production had leaf proline content much increased. The chlorophyll fluorescence responses to high temperature were used to determine heat tolerance of potato plants. At 3 hours of 40℃ in dark, ‘Kennebec’ showed more reduction in Fv/Fm and ΦPSII than other 3 lines examined. The Fv/Fm value of ‘Atlantic’ dropped to the lowest at 6 hr of treatment, and all 4 variety/lines showed similar Fv/Fm and other parameters then. The same 4 potato variety/lines were examined under temperature treatments of 20℃ and 30℃ for 3 weeks. The Fm of all 4 at 30℃ were lower than at 20℃. ‘Kennebec’ had the lowest Fo. At 30℃ for 21 days, three variety/lines showed significant reduction in Fv/Fm and both ‘Atlantic’ and ‘Kennebec’ had a value less than 0.8. ‘Kennebec’ also had the lowest ΦPSII value. At harvest, the shoot fresh weight of both ‘Atlantic’ and ‘Kennebec’ was reduced by more than 70%, and no tuber was produced in ‘Kennebec’. The other two lines at 30℃ produced 55% of shoot and 30% of tuber fresh weight obtained at 20℃. The Fv/Fm of the same leaf was monitored for one week on 6 potato lines grown under 20/15℃ and 30/25℃. The value declined under 30/25℃ treatment at one day in 97.1-19, at 4th day in LT-7 and ‘Kennebec’ and 7th day in 97.1-47, and the latter had the highest shoot and tuber fresh weight at harvest. 97.1-47 kept similar ratio of shoot to tuber fresh weight under both 20/15℃ and 30/25℃. The Fv/Fm values of 14 potato lines examined in field ranged between 0.46 and 0.70. Among them, ‘TN 1’ had higher Fv/Fm value than ‘TN 3’. To evaluate the vegetative growth of potato under heat stress, two clones were grown at 35/30℃, 30/25℃ or 20/15℃. Plants at 35/30℃ for 14 days had the smallest plant height and leaf SPAD values. The temperature of 30/25℃ restricts haulm growth, resulting in 70% of the shoot fresh weight of 20/15℃ treatment and very limited tuberization. Under 35/30℃ treatment, leaf SPAD value rapidly decreased and there was no tuberization. In all, potato clones like 07-237-1 (97.1-45)、PS3-2、06-674 and 97.1-47 showed physiological response related to better heat tolerance than ‘Kennebec’.
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