Effects of Light Intensity Gradient and Nitrogen Addition on Photosynthetic Characteristics and Antioxidant Enzyme Activities of Dicranopteris dichotoma

To explore the response of Dicranopteris dichotoma to the change of environmental resources, 3 light intensities and 2 nitrogen levels were set up to form treatments by a pot experiment. The effects of light intensity and nitrogen addition on photosynthetic characteristics and antioxidant enzyme activities of D. dichotoma were studied. The results showed that without nitrogen application, A_max was the largest under L2 shading, and the light utilization range was 19.2−1 138.7 μmol/(m²·s), larger than that under L1 and L3 shading. The A_max and utilization range of light energy under L1 and L2 shading conditions were improved after nitrogen application. And the decrease of A under L3 shading was caused by stomatal limitation. Without nitrogen application, MDA content, SOD activity, POD activity and CAT activity were significantly higher than those of L1 and L2 under L3 shading. Compared with non-nitrogen application, MDA content decreased under L1 and L3 shading, increased significantly under L2 shading, SOD, POD and CAT increased significantly. In conclusion, L2 shading was the most suitable condition for the growth of D. dichotoma, and L3 shading was the most serious condition for membrane peroxidation. Nitrogen application reduced the degree of membrane peroxidation under L1 and L3 shading.