Influences of Air Temperature on the Progress of Growth Stage and Freezing Hardiness in Over-Wintering Tea [Camellia sinensis (L.) 0. Kuntze] Bud(Agronomy)

Abstract

In this study, the progress of growth stage and change in freezing hardiness of tea [Camellia sinensis (L.) O. Kuntze] bud were examined from January to April in relation to air temperature for 10 years. The growth stage was shown by days to 70% sprouting at 25°C under 14-hour day length (DTS) . In the buds examined in January, DTS was over 15 days. DTS decreased as the time of examination was delayed and was only a few days in the buds examined in late March. The higher the average air temperature in late January, the longer the DTS in mid-February, but the higher the average air temperature after mid-February, the shorter the DTS later in the season. Freezing hardiness was shown by LT5 [lethal temperature (°C) of 50% buds] . It was the lowest in January, increased after mid-February, and reached - 5°C around a sprouting time. The average air temperature in early January showed a negative correlation with LT5 at later season, but that after late February showed a positive correlation in most cases. Thus the progress of growth stage and the decline of freezing hardiness were caused by increasing in air temperature after mid-February and late February, respectively. The LT50 of the buds at a certain growth stage varied with the year, suggesting that the freezing hardiness was also influenced by some factors other than the growth stage.