Abstract: We compared leaf anatomical structure, carbon (C), nitrogen (N) and phosphorus (P) concentration and their stoichiometry of wild ancient tea trees (Camellia talinensis) along an altitudinal gradient (2050, 2200, 2350, 2500 m) of Qianjiazhai Reserve in Ailao Mountain to clarify the response and adaptation of tea trees to environmental changes. The results showed that the thickness of leaf and diverse tissues (epidermis, cuticle, palisade tissue, sponge tissue, main vein) and C concentration showed a uni-modal pattern with rising altitude and peaked at altitude of 2200 m, suggesting that the environment at 2200 m altitude was conducive to the wild ancient tea trees for carbon assimilation, growth, and metabolism. The leaf structure became more compact and the concentrations of C, N and P in leaves showed a trend of increase, which would help tea trees adapt to the environment at high altitude. The anatomical indices showed a medium variation and exhibited high plasticity across the altitudinal gradient. Moreover, the growth of wild ancient tea trees in this region was not limited by N and P availability. The differences in either anatomical structure or stoichiometry of wild ancient tea trees across the altitudinal gradient might play a significant role in adapting to the vertical gradient niche.

Key words: wild ancient tea tree, altitude, anatomical structure, nutrition element, stoichiometry.