Objective A cold-injury index for Camellia sinensis cv. Fuding-dabaicha, the major tea cultivars in Guizhou, was established to provide the meteorological information for precision insurance actuary and agro services on the crop.
Method Physiological indices that reflect the growth of the tea plants under simulated low-temperatures in an artificial climate chamber were monitored. Semi-lethal temperature of the plants by cold stress was mathematically determined on a logistic function between the rate of injured cell and treatment temperature.
Result With the lowering temperature, the physiological responses of the plants showed a gradually increased SOD activity, initially raised and then declined MDA, and continuously increased relative electric conductivity. The semi-lethal temperature of the plants differed depending upon the duration of cold treatment. The longer the plants were exposed to the chill, the higher the semi-lethal temperature became. When the cold lasted for 3 d, 5 d, and 7 d, the semi-lethal temperatures rose to 1.5℃, 1.8℃, and 2.6℃, respectively.
Conclusion The growth responses of C. sinensis under low-temperature closely related to severity as well as duration of the exposure. At a temperature below 3℃, the harm imposed on the plant was more serious than above 3℃. And, a severe cold-injury would likely to incur if the treatment lasted for 7 days than 3 d or 5 d on the plants. The semi-lethal temperature of a plant increased with prolonged cold exposure. Thus, the cold-injury index should be applied with a consideration of local climatic conditions.
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