Effect of Nitrogen Forms on Photosynthetic Characteristics and Nitrogen Metabolism of Clematis

Abstract:

In order to understand the photosynthetic characteristics and response mechanism of nitrogen metabolism in Clematis, the growth, light response curve, A-Ci curve and nitrogen metabolism related enzyme activities of 1-year-old Clematis crassifolia and C. paten ssp. tientaiensis were studied under different ratios of NH₄⁺-N:NO₃^--N. The results showed that the ratio of NH₄⁺-N:NO₃^--N significantly affects the biomass and chlorophyll content of clematis, and the biomass, Chl a, Chl b, and Car contents of C. crassifolia reach the maximum under the ratio at 1:1, while the Chl a and Chl b contents of C. paten ssp. tientaiensis reach the maximum under the ratio at 1:3. Under the ratio of 1:1, the light saturation point (LSP) of C. crassifolia and the light compensation point (LCP) of C. paten ssp. tientaiensis were the maximum, and the V_cmax and J_max values of C. crassifolia leaves were significantly higher than those under other ratios. The glutamine synthetase (GS) activity of C. paten ssp. tientaiensis was the highest under the ratio of 3:1, while NR and nitrite reductase (NiR) activities under the ratio at 1:3 were significantly higher than those under other ratioes. Therefore, the mixed application of NH₄⁺-N and NO₃^--N could effectively promote the growth and photosynthesis, and enhance the nitrogen utilization efficiency of two Clematis. C. crassifolia was suitable for 1:1 of NH₄⁺-N to NO₃^--N, while C. paten ssp. tientaiensis was more suitable for 1:3.