Effects of Combined Copper and Zinc Stress on the Seed Germination, Seedling Growth and Cotyledon Physiological Metabolism of Chinese Flowering Cabbage

Purpose To study the effect of combined copper and zinc stress on the seed germination, seedling growth and cotyledon physiological metabolism of Chinese flowering cabbage to explore copper and zinc concentration scope of Chinese flowering cabbage’ growth.

Method By seed sprouting test, taking Chinese flowering cabbage as test material and combined copper and zinc as a variable, the effects of combined copper and zinc stress(eight treatments of combined Cu²⁺ and Zn²⁺ were 0 mmol/L + 0 mmol/L, 0.20 mmol/L + 0.17 mmol/L, 0.40 mmol/L + 0.34 mmol/L, 0.80 mmol/L + 0.68 mmol/L, 1.20 mmol/L + 1.02 mmol/L, 1.60 mmol/L + 1.36 mmol/L, 2.00 mmol/L + 1.70 mmol/L and 2.40 mmol/L + 2.04 mmol/L) on seed germination and seedling growth of Chinese flowering cabbage were studied.

Results With the aggravation of combined copper and zinc stress, the SOD and CAT activities, contents of soluble sugar, soluble protein and proline of Chinese flowering cabbage cotyledon decreased after initial increase, which reached the peak value of 30.76 U/(g·min), 327.81 U/(g·min), 11.24 nmol/g, 15.46 mg/g and 452.96 μg/g with treatment T4. The MDA content and O₂^– producing rate increased after initial decrease, which reached the bottom of 15.17 nmol/g and 17.86 nmol/(g·min) with treatment 4 and the POD activity and the relative conductivity increased gradually. The germination rate, seedling height, the longest root, fresh weight per plant and photosynthetic pigment contents of cotyledon decreased gradually, which reached the peak value of 68.00%, 1.64 cm, 2.99 cm, 18.32 mg, 0.79 mg/g, 0.20 mg/g, 0.99 mg/g, 0.19 mg/g with treatment T1(CK).

Conclusion Combined copper and zinc stress could stop the seed germination and seedling growth of Chinese flowering cabbage, and the tolerance of Chinese flowering cabbage to lower copper and zinc (0.80 mmol/L Cu²⁺ + 0.68 mmol/L Zn²⁺) in adversity was observed.