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Figure 1. 

Growth of Cyclocarya paliurus seedlings under different shading levels. (a), (c) Seedling growth in plastic greenhouse under three shading levels; (b), (d) seedling growth in plastic greenhouse under SH1 and SH0, respectively; SH0 indicates seedling growth with no shade net (about 60%−70% of full sunlight); SH1 indicates seedling growth with one layer of shade net (about 30%−40% of full sunlight); SH2 indicates seedling growth with two layers of shade net (about 10%−20% of full sunlight). Seedlings were treated in plastic greenhouses with different shading levels for 100 d (from June to September), and plastic sheeting was not fitted around the plastic greenhouse and the shade net was set at 1.8 m height from the ground.

Figure 2. 

(a) Water content and (b) total soluble sugar content in Cyclocarya paliurus seedlings under different shading levels. SH0 indicates seedling growth with no shade net; SH1 indicates seedling growth with one layer of shade net; SH2 indicates seedling growth with two layers of shade net. * means significant differences (p < 0.05 according to Tukey's HSD) between SH0, SH1 and SH2.

Figure 3. 

Chlorophyll content and carotenoid content in Cyclocarya paliurus leaves under different shading levels. (a) Chlorophyll content; (b) chlorophyll a content; (c) chlorophyll b content; and (d) carotenoid content. SH0 indicates seedling growth with no shade net; SH1 indicates seedling growth with one layer of shade net; SH2 indicates seedling growth with two layers of shade net. * means significant differences (p < 0.05 according to Tukey's HSD) between SH0, SH1 and SH2.

Figure 4. 

MDA content in Cyclocarya paliurus leaves under different shading levels. SH0 indicates seedling growth with no shade net; SH1 indicates seedling growth with one layer of shade net; SH2 indicates seedling growth with two layers of shade net. * means significant differences (p < 0.05 according to Tukey's HSD) between SH0, SH1 and SH2.

Figure 5. 

Mineral contents in Cyclocarya paliurus seedling under different shading levels. (a) mineral contents in seedlings; (b) translocation factor; (c) K content; (d) Ca content; (e) Mg content; (f) Na content. SH0 indicates seedling growth with no shade net; SH1 indicates seedling growth with one layer of shade net; SH2 indicates seedling growth with two layers of shade net. * means significant differences (p < 0.05 according to Tukey's HSD) between SH0, SH1 and SH2.

Figure 6. 

Variations in antioxidant enzyme activities in Cyclocarya paliurus leaves under different shading levels. (a) CAT activity; (b) PPO activity; (c) POD activity; and (d) SOD activity. SH0 indicates seedling growth with no shade net; SH1 indicates seedling growth with one layer of shade net; SH2 indicates seedling growth with two layers of shade net. * means significant differences (p < 0.05 according to Tukey's HSD) between SH0, SH1 and SH2.

Figure 7. 

(a) Correlation analysis and (b) network analysis between different studied factors. LA, DH, RH, DF, RSR indicates leaf area, ground diameter, the growth rate of shoot, the ratio of dry mass to fresh mass, the ratio of underground weight to aboveground weight, respectively; WC, TSS, Chl, PPO indicate water content, total soluble sugar content, Chlorophyll content, polyphenol oxidase activity;* represents significant differences (p < 0.05 according to Tukey's HSD) between SH0, SH1, and SH2. antioxidant enzyme; mineral content; physiological index; MDA content. Blue line means a positive relation between each other; red line means a negative relation between each other.