Assessment on the heat tolerance of lettuces seedlings by electrolyte leakage ratio

• Main Authors: Li, zhi-zhong, 李志中
• Other Authors: Hung, chin-Hsiung
• Format: Others
• Language: zh-TW
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/58522256764948321332

碩士 === 國立嘉義大學 === 園藝學系研究所(Graduate Institute of Horticultural Sc === 98 === Different lettuce cultivars were served as the material for the field trial and heat tolerance trial. The response of different cultivars in field trial (included of cultivars, fertilizer and shading) could be applied to the cultural practice in the production. The electrolyte leakage ratio of different lettuce cultivars were obtained by different heating temperature and time, then could be evaluated on heat tolerance of lettuce cultivars. The yield trial of six lettuce cultivars were treated with 3 shading treatments and 4 fertilizer formula in summer and winter season, Six lettuce cultivars had higher yield in winter than in summer. Under winter natural condition, Treatment applied with NPK 20-20-20 fertilizer could obtain highest yield of all the treatments, treatment applied with NPK 20-20-20 fertilizer was the next. ‘Sharp leaf lettuce’, ‘Dalumei’ and ‟Head lettuce’ had higher yields in winter; but ‟Dalumei’ also had higher yield in summer. Under summer natural condition, treatments with NPK 20-20-20 fertilizer had better yield than other treatments, but fertilizer treatments had no significant difference one another. ‘Dalumei’ (42.3 g) lettuce were the cultivar with high and stable yield. Treatments with 50％ and 70％ shading had seriously affected yield, leaves number, top weight, growth characteristics of six lettuce cultivars. Electrolyte leakage ratio could be used to assess the damage of cell membrane by heating temperature and time. Then electrolyte leakage ratio of four lettuce cultivars (Leaf lettuce ‘V-155’, asparagus lettuce ‘V-305’, lettuce-41, Wrinkle leaf lettuce ‘LS-005’) were evaluated in order to distinguish the difference of cultivars under heat stress condition. Plug seedling at 5-6 true leaf stage, the 3rd and 5th leaf of each cultivar were punched to 1cm round leaf disc and then 5 leaf disc were placed in a water bath at 30-70℃ for 1-8 hours and at 50℃ for 1-8 hours for testing electrolyte leakage ratio. The curve of electrolyte leakage ratio were sigmoidal in all treatments. The 3rd leaf treated with water bath at 50℃ for 80 minutes were typical and could distinguish the difference of cultivars. Four lettuce cultivars could be separated by electrolyte leakage ratio, and ranked as follow: asparagus lettuce ‘V-305’≦Leaf lettuce ‘V-155’＜Lettuce-41＜Wrinkle leaf lettuce ‘LS-005’. The electrolyte leakage ratio of 37 lettuce cultivars could be were distinguished by treating at 50℃ water bath for 80 minutes, four lettuce cultivars (Leaf lettuce ‘V-155’, asparagus lettuce ‘V-305’, ‘lettuce-41, ‘Wrinkle-leaf lettuce ‘LS-005’) were served as contol, and. Membrane thermal stability of 3rd leaf were more stable than 5th leaf of lettuce seedling in all the treatments. electrolyte leakage ratio of ‘Taiwan large-leaf white lettuce’, ‘Cream 164’, ‘Asparagus lettuce ’ were the lower than other cultivars and ‘Sharp leaf lettuce’. The electrolyte leakage ratio of ‘United States Great Lakes 659 M. T. head lettuce’, ‘Lettuce-180’, ‘Wrinkle-leaf lettuce ’ were significantly higher than other cultivars and ‘Wrinkle leaf lettuce’. Four lettuce cultivars treated with heat stress at 30℃, 35℃ and 40℃ for 1-4 hours, The electrolyte leakage rate of four lettuce cultivars were ranked from low to high respectively：Asparagus lettuce≦Leaf lettuce＜Lettuce-41＜Wrinkle leaf lettuce. Four lettuce cultivars treated with Salicylic acid then put into 35℃ heat stress for 1-4 hours, The electrolyte leakage rate of ‘Leaf lettuce’ were 16.1％ at 1st and 2nd hours of heat stress, that of ‘Asparagus lettuce’ were 12.8％ at the 3rd and 4th hours. ‘Lettuce-41’ and ‘Wrinkle leaf lettuce’ were seriously affected, electrolyte leakage rate of ‘wrinkled leaf lettuce’ increased from 34.1％ to 39.9％ at 2nd hours and reduced to 29.3％ at 3rd hours. After treating with 40℃ and 45℃ heat stress, the electrolyte leakage rate of ‘wrinkled leaf lettuce’ decreased greatly at 4th hours. Salicylic acid treatment had thermal protection to reduce heat damage under high temperature stress condition.