Response of leaf photosynthetic characteristics of Cotinus coggygria to combined application of mineral nitrogen, phosphorus and potassium

  Objective  Relationship between photosynthetic characteristics and combined application of mineral nitrogen, phosphorus and potassium (N, P and K) has been studied to provide nutrient management strategies of Cotinus coggygria.

  Method  Under 10 treatments (see below), the photosynthetic pigment, leaf area, diurnal variation of photosynthetic parameters and light response curve of leaves of potted C. coggygria seedlings were measured, and theses generated data were then related to combined application of N, P and K. With a L9 (3⁴) orthogonal design for N (0, 6, 12 g/plant), P (0, 10, 20 g/plant) and K (4, 8, 12 g/plant), these 10 treatments were T1 (N₁P₁K₁), T2 (N₁P₂K₂), T3 (N₁P₃K₃), T4 (N₂P₁K₂), T5 (N₂P₂K₃), T6 (N₂P₃K₁), T7 (N₃P₁K₃), T8 (N₃P₂K₁), T9 (N₃P₂K₁) and T10 (N₀P₀K₀).

  Result  Under each treatment, the net photosynthetic rate (P_n) and stomatal conductance (G_s) had a “double peak curve” change, while the transpiration rate (T_r) had a “single peak curve” change. The contents of total chlorophyll and carotenoid were higher under T5, T6 and T8 than under other treatments. Except for T2, the daily average value of P_n was significantly higher than control (P < 0.05). Among all the 10 treatments, T9 had the highest performance on all the tested diurnal variation parameters (G_s, P_n, T_r and light energy use efficiency (LUE)), and the daily average values of light response parameters (maximum net photosynthetic rate (P_nmax), light saturation point (LSP), light compensation point (LCP) and dark absorption rate (R_d)). In addition, the redundancy analysis showed that the contribution rate of fertilizer was P > N > K, while P had a greater effect on photosynthetic pigments (Chl s and Car) and a positive correlation with P_n, P_nmax and LSP. In contrast, N and K had greater influences on LUE, which was positively correlated with LCP, T_r and G_s.

  Conclusion  Results from this experiment demonstrate that among the tested 10 NPK treatments, T9 (12 g/plant N, 20 g/plant P and 8 g/plant K) is the optimal fertilization to significantly promote leaf photosynthetic capacity of C. coggygria.