| In this study, Longjing 43 tea in Zhejiang was studied as test materials, 34℃/25℃,38℃/29℃and 42℃/33℃ temperature was treated between day and night in three different treatment,26℃/17℃ was taken as contral, each high temperature separately continued 0 days,3 days,6 days,9 days, and resumed for three days, photosynthesis and fluorescence characteristics, enzyme activities and relative electrical conductivity was measured, as well as internal quality changes. The test results were as follows:(1)The chlorophyll a, chlorophyll b and carotenoid content of Longjing decreased with the extension of high temperature treatment, when dealing with the same time. The average of net photosynthetic rate under high temperature processing of tea from high to low were CK treatment 34℃/25℃ treatment> 38℃/29℃ treatment> 42℃/33℃ treatment. The light saturation point and apparent quantum efficiency decreased under high temperature treatment while light compensation point increased after high temperature; Fv/Fm decreased with the extension of high temperature treatment, when dealing with the same time, Fv/Fm values had the maximum reduction than control under 42℃/33℃ treatment.(2)The activity of POD and CAT of Longjing 43 incereased with the extension of the high temperature treatment time under 34℃/25℃ and 38℃/29℃ treatment at first and then increased and then decreased, the activity of SOD decreased firstly, and then increased, then decreased, during recovery, had a significant degree of recovery; The activities of SOD, POD and CAT were firstly increased and then decreased of 42℃/33℃ treatment, during recovery trend showed almost no recovery. MDA content of Longjing 43 continued to rise after each heat treatment. The activity of PAL firstly increased and then decreased,34℃/25℃ and 38℃/29℃ treatment during recovery can be basically restored to the control level,42℃/33℃ treatment had no significant restore. The relative electrical conductivity of cells increased with the extension of treatment time. The average of the relative electrical conductivity of cells under high temperature processing of tea from high to low were CK treatment 34℃/25℃ treatment>38℃/29℃ treatment>42℃/33℃ treatment.(3) The study found that high temperatures would not only affect the quality of the summer tea, but also reduce the ingredients taste of next spring. With the extension of the duration of the high temperature, the water extracts, free amino acids, soluble sugar content decreased, polyphenols, caffeine content increased, the soluble protein content increased first and then decreased.34℃/25℃ treatment had the minimum reductions of water extracts, free amino acids and soluble sugar content among 34℃/25℃,38℃/29℃ and 42℃/33℃ treatment,42℃/33℃ treatment had the maximum reductions; 34℃/25℃ treatment had the minimum increment of polyphenols, caffeine content among 34℃/25℃,38℃/29℃ and 42℃/33℃ treatment,42℃/33℃ treatment had the maximum increment; The maximum degree of recovery 34℃/25℃ during the recovery process maximum,38℃/29℃ followed, 42℃/33℃ minimum degree of recovery. Quality of 34℃/25℃ treatment is better than quantity of spring tea under 38℃/29℃ treatment.(4) By analyzing the correlation between the quality of each component and physiological parameters, we found the correlations among chlorophyll content, photosynthetic parameters, fluorescence parameters, MDA and phenylalanine ammonia-lyase, water extracts, polyphenols and free amino acids were larger. Based on the changes of phenol ammonia ratio of Longjing tea leaves, a series of physiological relevance of the larger index as a reference to calculate the temperature of tea stress index, according to the index, we divided the hot disaster high-temperature in summer Longjing tea harm divided into mild, moderate, severe, extremely heavy four species level, and we got high temperature and duration metrics of each class. |
