Abstract: To explore the adaptive mechanism of physiological growth of tea plants under different bamboo density conditions, three treatments, namely T1, T2 and T3, were set in the natural mixed forest of moso bamboo (Phyllostachys edulis) and tea plants [Camellia sinensis (L.) O. Kuntze] in the Mogan mountain area of Zhejiang Province, with bamboo densities of 1 200 plants·hm^-2, 1 800 plants·hm^-2 and 2 400 plants·hm^-2, respectively, and 3 000~3 300 plants·hm^-2 as the control (CK). Tea yield was evaluated, nitrogen, phosphorus, nonstructural carbohydrates (NSC) and biomass distribution of tea tree were determined, root morphology, distribution and architecture were analyzed, and quality indicators of tea such as amino acids, theanine and tea polyphenols were tested after 2 years of cultivation. The results show that (1) compared to CK, T2 and T3 treatments significantly increased tea yield by 15.96% and 18.8%, respectively, increased biomass of leaves and lateral roots, and increased the nitrogen, phosphorus and NSC contents in leaves, (2) T1, T2 and T3 treatments significantly increased the root length, root surface area and root length ratio of the >0-1 mm diameter grade in 0-20 cm soil layer, reduced root diameter and root length ratio of thick roots (diameter>2 mm) in 0-20 cm soil layer, increased the contents of starch and soluble sugars in lateral roots, reduced the topological index of the whole root system and increased the root tips and root fractal dimension, (3) T1 and T2 treatments significantly increased the contents of amino acids, caffeine and tea polyphenols and water extract, and reduced the polyphenols-amino acid ratio. In conclusion, reasonable control of bamboo density can promote the growth of tea plants and improve the tea yield effectively. Tea plants promote the growth of leaves and lateral roots by increasing nitrogen, phosphorus and non-structural carbohydrate accumulation in leaves and lateral roots and promote root encroachment of surface soil space by increasing the proportion of fine roots, enhancing the root branch strength, reducing the cost of root construction to accommodate moderate closure conditions and interspecific competition strength. The conclusion can provide scientific basis for the management of innovation mode of tea plants under the moso bamboo forest.

Key words: tea plant, moso bamboo, under-forest economy, physiological growth, tea quality