关键词: 茶树, 叶片, 海拔, 越冬期, 生理特性, 细胞结构

Abstract: To clarify the low‑temperature stress response mechanisms of tea plants at different altitudes，we studied the Xinyang group species in the Shihe District of Xinyang City，Henan Province，at altitudes of 100 m and 600 m. We analyzed the photosynthetic characteristics，antioxidant enzyme activities，membrane lipid peroxidation levels，and tissue cell structure changes of tea leaves during the overwintering period. Results showed that during the pre‑winter（T1），mid‑winter（T2），and late‑winter（T3）stages，the net photosynthetic rate of low‑altitude tea plants was 0.6，1.5，and 1.2 times higher than that of high‑altitude tea plants，respectively. Chlorophyll content in low‑altitude plants was 36.91% and 48.19% higher than in high‑altitude plants during T2 and T3.Low‑altitude plants also exhibited more intact chloroplast structures.Throughout the overwintering period，superoxide dismutase（SOD）activity in leaves of tea plants at both altitudes first increased and then decreased，peaking in T2.During T1，T2，and T3，SOD activity in high‑altitude tea leaves was 25.20%，27.05%，and 20.59% higher than in low‑altitude tea leaves，respectively.However，catalase（CAT）activity in high‑altitude tea leaves was 27.27%，29.48%，and 26.64% lower than in low‑altitude leaves. Peroxidase（POD）activity showed a trend similar to that of CAT activity.The malondialdehyde（MDA）content of high‑altitude plants in T2 and T3 was significantly higher than that of low‑altitude plants，increasing by 72.21% and 77.04%，respectively.Structural observations revealed that the mesophyll thickness of high‑altitude tea plants increased significantly in T2 and T3，rising by 10.19% and 10.47% compared to T1.The stomatal opening rate and open area of high‑altitude plants decreased significantly in T2.Compared between the two altitudes，low‑altitude tea leaves had higher cell wall thickness and stomatal density，averaging 36.92% and 22.52% higher than high‑altitude tea leaves，respectively.In conclusion，low‑altitude tea plants adapt to low‑temperature environments by maintaining high photosynthetic efficiency and antioxidant capacity，as well as by enhancing cell wall and stomatal structures.In contrast，high‑altitude tea plants optimize water management by increasing mesophyll thickness and adjusting stomatal opening，although this may come at the cost of reduced photosynthetic efficiency.

Key words: Tea plant, Leaf, Altitude, Overwintering stage, Physiological characteristics, Cellular structure