Role of Chitosan in the Regulation of the Growth, Antioxidant System and Photosynthetic Characteristics of Maize Seedlings under Cadmium Stress

Cadmium (Cd) pollution was becoming more and more serious; there is an urgent need for an effective solution to inhibit the harm of cadmium stress. Chitosan (CTS) is a biologically active polysaccharide that plays a unique role under abiotic stress. So it was of much improtance to explore the effects of CTS on maize resistance ability. The results showed that maize (Zea mays L.) seedling growth was significantly inhibited, root system was the first organ that contact with cadmium stress, so the roots accumulated a lot of cadmium content, reducing the root activity, root growth was blocked, which led a reduction in nutrients to the leaves, and the chlorophyll content and photosynthetic enzyme activity were decreased. Additionally, the antioxidant enzyme activity was reduced. Under cadmium stress, CTS treatments significantly increased the growth rate and compensated for the function of root system, and which increased SOD, POD, CAT, APX and GR activities and AsA, GSH contents of leaves, but reduced \({\text{O}}_{2}^{{\centerdot \, - }}\), H₂O₂ and MDA contents. CTS increased chlorophyll content, P_n, G_s, T_r, F_v/F_m, Φ_PSII, qP and NPQ, reduced C_i, avoided excessive light damage and maintained higher PSII activity. CTS alleviated the destruction of antioxidant enzymes and inhibited the production of reactive oxygen species, which improved the chlorophyll content and photosynthesis of plants. Our results showed that CTS could be used in cadmium-contaminated areas to reduce the toxicity of cadmium stress. The study results provide a theoretical and experimental basis for the safe production of maize in cadmium-contaminated areas.