| Summary: | 碩士 === 國立中興大學 === 生命科學系 === 92 === The aim of this study focus on the photosynthesis, accumulation of carbohydrate and heat tolerance of difference pear (Pyrus) grafting combinations. The results showed that the branch of both P. koehnei and ‘Laio Li’ accumulated higher carbohydrate than that of ‘Heng Shan’ in the branch when they were grafted to ‘Tan Li’ rootstock. Furthermore, accumulated carbohydrate in the branch of P. koehnei was higher that that of ‘Laio Li’. The growth potential of ‘Heng Shan’ was higher in which one branch was grafted with ‘Laio Li’ for 5 years than that no grafted. However, photosynthetic rate of leaf area unit of ‘Laio Li’ leaves was higher than that of P. koehnei, when they were grafted to ‘Heng Shan’. Above results indicated that the branch of grafted P. koehnei accumulated more photosynthate was not due to the higher photosynthetic rate of leaf area unit rather than higher leaf number as well as longer leaf span. In spite of the temperature tolerance of photosystem Ⅱ estimated from chlorophyll fluorescence was not significant difference among P. koehnei, ‘Heng Shan’ and ‘Sinkou’ pear, the optimum temperature for photosynthesis of P. koehnei leaves was higher than that of both ‘Heng Shan’ and grafted ‘Sinkou’. This result demonstrated that P. koehnei leaves could maintain higher photosynthesis rate during high temperature period in Central of Taiwan. From the above results it could be considered that P. koehnei might be used as a carbon source for pear production under increasing temperature of global climate change.
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