Abstract: Understanding frost damage level for different tea cultivars is of great significance for the precise forecasting of spring frost damage to tea plants. In this study, pot-grown “Longjing 43” and “Baiye No. 1” tea plants were subjected to five low-temperature treatments (4, 2, 0, -2, -4 ℃） and 25 ℃ (control) and eight low-temperature duration treatments (0.5, 1, 2, 3, 6, 9, 12, and 24 h) during the spring bud sprouting stage in an artificial climate chamber. The effects of low-temperature stress on the phenotypic characteristics and tea quality of the plants were examined. Based on a comprehensive consideration of minimum temperature and exposure duration, frost damage grading indices for “Longjing 43” and “Baiye No. 1” were established. The results showed that: (1) there were significant differences in phenotypic characteristics between “Longjing 43” and “Baiye No. 1” after lowtemperature stress. Starting from 0 ℃, as temperature decreased and the exposure duration increased, the phenotypic changes in “Baiye No. 1” were noticeably more severe than those in “Longjing 43”, indicating that “Longjing 43” had stronger cold resistance than “Baiye No. 1”. (2) Under low-temperature stress, tea quality of “Longjing 43” exhibited distinct change patterns. At temperatures of 0 ℃ and above, polyphenol content showed a slow declining trend with increasing exposure time. When the temperature dropped below 0 ℃, the content generally increased. In contrast, amino acid content showed a slow increasing trend at temperature above 0 ℃, while at temperatures below 0 ℃ it initially increased, then declined, and subsequently increased slowly again. (3) Using hourly temperature data from tea garden microclimate stations in 2016 and from 2021 to 2022, the frost damage grading indices for “Longjing 43” and “Baiye No. 1” were validated, achieving accuracy of 100% and 88.89%, respectively.

Key words: Longjing 43, Baiye No. 1, low temperature stress, tea quality, spring frost damage, meteorological index, rank division