Abstract: To investigate the effects of phosphorus-aluminum interaction on the growth of tea plants, phosphorus and aluminum interaction treatments with three aluminum concentrations and five phosphorus concentrations were set to analyze the changes in root growth, secretion of organic acids and uptake of phosphorus and aluminum in tea plants. The results show that both low phosphorus (0.01 mmol∙L^-1) and high aluminum (1 mmol∙L^-1) significantly promoted the growth of new roots in tea plants, and the number of root tips, root length, average diameter and increase of dry matter in new roots reached the maximum under the combined treatment of low phosphorus and high aluminum. High aluminum was able to restore the growth of new roots impeded by high phosphorus (0.5 mmol∙L^-1) conditions. In addition to the high phosphorus treatment (0.5 mmol∙L^-1), increasing the concentration of phosphorus or aluminum in the environment could significantly promote their accumulation in the roots of tea plants. Within a certain range, phosphorus significantly promoted the accumulation of aluminum in shoots. However, aluminum inhibited the accumulation of phosphorus in shoots when phosphorus was sufficient (>0.05 mmol∙L^-1). When phosphorus was sufficient, high aluminum promoted the secretion of oxalic acid, malic acid and citric acid. Phosphorus application promoted the secretion of citric acid, while low phosphorus promoted the secretion of oxalic acid and malic acid. Low phosphorus and high aluminum synergistically promoted the secretion of malic acid. The results of two-way ANOVA show that phosphorus and aluminum concentrations and their interaction had highly significant effects on root length, root tip number, phosphorus and aluminum uptake and organic acid secretion in tea plants (p<0.01), which showed that phosphorus and aluminum interaction can affect root growth and organic acid secretion of tea plants significantly.

Key words: tea plant, root, phosphorus and aluminum interaction, organic acid secretion