Abstract:

Objective: This paper aimed to explore the effect of combined application of nitrogen, phosphorus and potassium on the growth and leaf color of Cotinus coggygria, and to solve the problems of poor growth and dim leaves of C. coggygria in autumn and winter. Method: In this study, 4-year-old potted seedlings of C. coggygria were used as experimental materials. Three factor and three-level orthogonal design experiments were carried out with urea (N 0, 7.5, 15 g·plant^-1), calsium superphosphate (P 0, 12.5, 25 g·plant^-1) and potassium sulfate (K 5, 10, 15 g·plant^-1). Plant height (H), ground diameter (D) and leaf area (LA), leaf color parameters, leaf pigments including chlorophyll (Chls), carotenoids (Car), and anthocyanins (Ant), soluble protein content (SP), soluble sugar content (SS), and phenylalanine ammonia-lyase(PAL)activity were measured under the different N, P and K combination conditions, and the relationships between N, P and K and plant growth or leaf color were determined. Result: 1) The reasonable combined application of N, P and K was able to promote the growth of C. coggygria. The increment of plant height in treatment T3(N₁P₃K₃) and T9(N₃P₃K₂) was significantly higher than that of the control (p < 0.05). Except for T5(N₂P₃K₃) and T7(N₃P₁K₃), the growth of ground diameter of other treatments was significantly higher than the control(p < 0.05). Except for T1(N₁P₁K₁), T4(N₂P₁K₂), and T8(N₃P₂K₁), the increment of leaf area in other treatments was significantly higher than that of the control (p < 0.05). 2) Reasonable combined application could also increase the pigment content of C. coggygria leaves. T6(N₂P₃K₁), T7, T8 and T9 treatments could significantly increase the total chlorophyll content in the vigorous growth stage and the mid-discoloration stage. T5, T7, T8 and T9 significantly increased carotenoids content in the vigorous growth stage. T3, T4, T5, and T6 significantly increased anthocyanins content at the terminal discoloration stage. 3) The results of the redundancy analysis showed that N and K were the main nutritional factors affecting height, leaf area, chlorophyll and carotenoids, while P was the main nutritional factor affecting ground diameter and anthocyanins. Anthocyanins was a key factor for red color of C. coggygria leaves, which was positively correlated with phenylalanine ammonia-lyase activity and negatively correlated with soluble protein and soluble sugar. Conclusion: The response of plant growth and leaf color to different ratio of N, P and K application is different. Within the scope of this experiment, T3 (N, P and K applying amounts of 0, 25, 15 g·plant^-1, respectively) and T9(N, P and K applying amounts of 15, 25, 10 g·plant^-1, respectively) promote both growth and leaf color. But in the long run, N deficiency would affect the growth of C. coggygria and affect the color quality of leaf, finally. Therefore, T9 treatment can maintain growth and color quality of leaf, and enhance the ornamental value.

Key words: Cotinus coggygria, N, P and K, growth, pigment content, physiological response