Studies on the Varietal Differences of the Cold-Resistance of the Tea Plant (Part 1)

Abstract

In January 1953, it was not so cold, and the winter buds commenced to grow up gradually, so we feared if they should be suffered from sudden severe cold. Taking this chance, we tried to examine if there existed any varietal difference in cold resistance of the tea buds.The branches of each variety with buds were gathered from the field in winter and spring, and part of them was tested the refractive index of the cell sap, and the rest was put into a refrigerator which was regulated at -5°C. After 1-, 3-, or 5-hours' treatment, they were put out and the, cold injury was examined. The varietal difference was evident which was positively correlated with the refractive index. Miyoshi was weakest and U-21 (triploid) and Yamatomidori were strongest.As the buds began to flush in spring, the refractive index and the cold resistance were gradually decreased, and the order of cold resistance among varieties was varied. This alteration seemed to be caused. by the varietal difference of activity of spring buds.In winter field, it was observed that nearly 20% of tea. buds were killed after severe cold attack, and so, it might be thought important to avoid non-winter-hardy varieties in such a district.