外源H2O2对盐胁迫下小白菜种子萌发和幼苗生理特性的影响

以小白菜"甜脆青"为试材,研究不同浓度（5、10、25、50和100 mmol/L）过氧化氢（H₂O₂）浸种处理对100 mmol/L NaCl胁迫下小白菜（Brassica chinensis L.）种子萌发、幼苗生长及生理特性的影响。结果表明：100 mmol/L NaCl胁迫明显抑制小白菜种子的萌发状况和幼苗生长,发芽势、发芽指数、活力指数及幼苗根和芽长度和鲜重均明显降低,根和芽中CAT的活性及K⁺含量明显受到抑制,渗透调节物质、活性氧和MDA含量显著增加。不同浓度H₂O₂浸种处理提高了NaCl胁迫下小白菜种子发芽势、发芽指数和活力指数,促进小白菜根和芽的生长,增强了NaCl胁迫下根和芽中SOD、CAT和APX的活性及K⁺含量,降低O₂^-·产生速率及H₂O₂和MDA含量,进一步促进脯氨酸和可溶性糖含量的增加,降低体内Na⁺含量。其中以10 mmol/L H₂O₂处理缓解盐胁迫效果最好,明显缓解NaCl胁迫对小白菜种子萌发和幼苗生长的抑制。

Effects of exogenous hydrogen peroxide on seed germination and physiological characteristics of pakchoi seedlings (Brassica chinensis L.) under salt stress

Salt stress imposes a major environmental threat to agriculture; therefore, efforts to increase salt tolerance of crop plants bear remarkable importance for sustainable agriculture on saline lands and could potentially improve crop yield overall. Pakchoi (Brassica chinensis L.) seeds were pre-treated with 5, 10, 25, 50 and 100 mmol/L hydrogen peroxide (H₂O₂) solution for 2 h to evaluate the effect of H₂O₂ on germination, early growth, and physiological characteristics of seedlings under 100 mmol/L NaCl stress. Results showed that 100 mmol/L NaCl stress inhibited pakchoi seed germination and seeding growth. Germination potential, germination index, vigour index, and root length were decreased significantly. The osmosis-regulating substance, reactive oxygen species (ROS), and malondialdehyde (MDA) content in roots and shoots of pakchoi was increased significantly. However, the activities of catalase (CAT) and K⁺ content in roots and shoots were strongly inhibited. Different concentrations of H₂O₂ (5, 10, 25, 50, and 100 mmol/L H₂O₂) increased the seed germination potential, germination index, and vigour index, and promoted the growth of pakchoi roots and shoots. Application of H₂O₂ also significantly enhanced the activities of antioxidant enzymes such as superoxide dismutase (SOD), ascorbate peroxidase (APX), and CAT, and decreased the contents of MDA and reactive oxygen species like H₂O₂ and O₂^-· in roots and shoots of pakchoi seedlings, and further increased the proline and soluble sugar contents. In addition, K⁺ content and K⁺/Na⁺ in roots and shoots of pakchoi seedlings were increased by H₂O₂; however, Na⁺ content was decreased. 10 mmol/L H₂O₂ showed the best effect for improving seed germination and seeding growth of pakchoi under NaCl stress. However, the mitigative effects of 100 mmol/L H₂O₂ on inhibition of pakchoi seed germination and seedling growth caused by NaCl stress were weakened. Hence, an appropriate concentration of H₂O₂ treatment improved NaCl tolerance of pakchoi plants by increasing the plant''s antioxidative defence system, the capacity for osmotic adjustment, and K⁺ content and decreasing the contents of ROS and Na⁺ to alleviate membrane lipid peroxidation, thereby increasing seed germination and seedling growth under NaCl stress.