Effects of low temperature stress on physiological characteristics of tea leaves(Camellia sinensis L.)

【Objective】 The reaserch on effects of differing low temperature stress on main osmotic adjustment substances,chlorophyll content(chlorophyll content index) and fluorescence paramerter Fv/Fm of tea leaves was performed to study the response of tea plants to low temperature stress and provide a basis for tea introduction and cultivation.【Method】 One-year-old detached branches of 'Shuchazao' and 'Wuniuzao' were treated under-6,-9,-12,-15 and-18 ℃,respectively,and the changes of relative conductivity,proline,soluble protein,soluble sugars,chlorophyll content and Fv/Fm of tea leaves under stress conditions were measured with untreated materials as control.Then the semilethal temperature(LT50) was calculated based on relative conductivity.【Result】 The results showed that there was no significant difference in relative conductivity between control and treatment under-6 ℃ stress,but the relative conductivity was remarkably increased with the decrease of temperature.As temperature decreased,the content of proline,soluble protein,soluble sugars all ascended first and then decreased,and these indexes of 'Shuchazao' exceeded significantly those in 'Wuniuzao'.However,temperature range in responsive to low temperature stress of these indexes was different between 'Shuchazao' and 'Wuniuzao'.'Shuchazao' had a remarkable higher content of Chlorophyll than 'Wuniuzao'.When the temperature was below-9 ℃,chlorophyll content index and Fv/Fm decreased obviously.LT50 of 'Shuchazao' and 'Wuniuzao' were-17.3 and-16.7 ℃ respectively.【Conclusion】 The physiological indexes related to cold-resisitance of tea plant all changed significantly under low temperature stress,and tea plant would suffer serious physiological harm at-17 ℃,which should be on guard on tea cultivation.