Regulation of chitosan on the ascorbate-glutathione cycle in Zea mays seedling leaves under cadmium stress

Zea mays L. seedlings of the variety ‘Zhengdan 958’ were used as experimental material to analyze the effects of the external application of chitosan on the activities of antioxidant enzymes and concentrations of nonenzymatic antioxidant substances in the ascorbate-glutathione (AsA-GSH) cycle, as well as on Z.mays seedling biomass, leaf cadmium content, superoxide radical (O₂^·-) production rate, and hydrogen peroxide (H₂O₂) content under cadmium stress. With the prolongation of cadmium stress, oxidative stress on the maize seedlings increased, whereas the activities of antioxidant enzymes (APX, GR, DHAR, MDHAR) and concentrations of antioxidants (AsA, GSH) in the leaves decreased. The excessive accumulation of cadmium eventually inhibited the growth of the Z.mays seedlings. Under cadmium stress, the application of chitosan reduced the production ratesof O₂^·- and H₂O₂ in the Z. mays seedling leaves and increased the activities of APX, GR, DHAR, and MDHAR and concentrations of AsA and GSH, reaching a maximum at 72 h. Chitosan promoted the regeneration of AsA and GSH and maintained the redox status of cells, which promoted the growth of aerial parts of the Z.mays seedlings. These results indicated that chitosan maintained a high AsA-GSH cycle efficiency, improved the antioxidant capacity of Z. mays seedlings, and effectively alleviated the inhibition of seedling growth under cadmium stress.