壳聚糖对镉胁迫下玉米幼苗叶片AsA-GSH循环的调控效应

以玉米（Zea mays L.）品种‘郑单958’为实验材料，分析外施壳聚糖对镉胁迫下玉米幼苗生物量、叶片镉含量、叶片超氧阴离子（O₂^·-）产生速率和过氧化氢（H₂O₂）的含量，以及抗坏血酸-谷胱甘肽（AsA-GSH）循环中抗氧化酶的活性及抗氧化物含量的影响。结果显示，随着镉胁迫时间的延长，玉米幼苗发生氧化胁迫，叶片抗氧化酶（APX、GR、DHAR、MDHAR）活性和抗氧化物（AsA、GSH）的含量降低，镉积累过量会抑制玉米幼苗的生长。施加壳聚糖可以降低镉胁迫下玉米幼苗叶片O₂^·-的产生速率和H₂O₂含量，提高上述抗氧化酶活性和抗氧化物的含量，促进AsA和GSH的再生，维持细胞的氧化还原状态，促进玉米幼苗的生长。研究结果表明壳聚糖处理后玉米幼苗保持了较高的AsA-GSH循环运作效率，提高了抗氧化能力，可有效缓解镉胁迫对玉米幼苗生长的抑制。

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.