Effects of Salicylic Acid on Growth and Physiology of Non-heading Chinese Cabbage Seedlings under Cadmium Stress

  Objective  Growth and physiological responses of non-heading Chinese cabbage to salicylic acid (SA) spraying under Cd-stress were studied.

  Method  Huaguan non-heading Chinese cabbage (Brassica chinensis L.) seedlings under an imposed stress of 50 mg CdCl·2.5H₂O·L⁻¹ were sprayed with SA at a rate of 0.01-0.5 mmol·L⁻¹. Growth, root activity, osmotic regulators, photosynthetic pigment content, malondialdehyde (MDA) content, and antioxidant enzyme activity as well as the Cd absorption, accumulation, and transportation of the separately treated seedlings were determined.

  Result  The seedlings under the Cd-stress control (CK₂) grew significantly slower with reduced root vitality, contents of photosynthetic pigments, protein, and proline (Pro), and antioxidant enzyme activities but increased MDA in comparison to the blank control (CK₁). Under the Cd-stress, SA spraying in the range of 0.01-0.05 mmol·L⁻¹ rejuvenated the seedling growth, with the greatest effect observed when 0.05 mmol·L⁻¹ SA was applied. The seedlings of CK₁ had their root/shoot ratio increased by 140%, proline content by 44.98%, POD by 118.18%, and CAT by 70.43% over those of CK₂ 10d under the Cd-stress, while the aboveground parts of the plants had the Cd content and transport coefficient significantly reduced. On the other hand, when higher SA concentrations in the range of 0.1-0.5 mmol·L⁻¹ was applied, the seedling growth was significantly inhibited.

  Conclusion  At a concentration of 0.05 mmol SA·L⁻¹, the spraying could effectively alleviate the Cd toxicity and improve the Cd tolerance of the non-heading Chinese cabbage seedlings.