研究了不同浓度Cr³⁺胁迫对苦草〔Vallisneria natans(Lour.)Hara〕叶片活性氧清除系统及细胞超微结构的影响。结果表明,随Cr3+浓度的提高(0.5~15.0 mg·L^{- 1}),苦草叶片中O^2.-.和MDA含量、SOD和POD及CAT活性均呈现先上升后显著下降的变化趋势,且在10.0和15.0 mg·L^{- 1}Cr3+胁迫条件下显著低于对照(P<0.05)。在1.0 mg·L^{- 1}Cr³⁺胁迫条件下,O^2.-.的含量达到最高(0.96 OD.g-1);在2.0 mg·L^{- 1}Cr3+胁迫条件下,MDA含量和SOD、POD及CAT活性最高。随Cr³⁺胁迫浓度的提高,苦草叶片细胞超微结构受损程度逐渐加深,导致核仁和高尔基体消失;线粒体脊突膨胀,线粒体膜受损并出现囊泡状结构;叶绿体变形、类囊体膨胀受损并最终导致叶绿体破损。表明高浓度Cr³⁺胁迫对苦草叶片细胞产生了不可逆的伤害。 

Effects of Cr³⁺ stress with different concentrations on the scavenging system of active oxygen and cell ultrastructure of Vallisneria natans (Lour.) Hara leaf were investigated. The results showed that the contents of O^2.-and MDA and the activities of SOD, POD and CAT presented a trend of increasing firstly and then decreasing with increasing of Cr³⁺ concentration (0.5- 15.0mg·L^{- 1}), and in 10.0 and 15.0mg·L^{- 1}Cr³⁺ stress conditions, these indexes were obviously lower than that of the control(P<0.05). The  O^2.-.content was the highest (0.96OD·g- 1)in 1.0mg·L^{- 1} Cr³⁺ stress condition, but the MDA content and the activities of SOD, POD and CAT reached the highest in 2.0mg·L^{- 1} Cr³⁺ stress condition. With increasing of Cr³⁺ concentration, the injury degree of cell ultrastructure of V. natans leaf became more severe, and resulted in the nucleolus and golgi apparatus disappeared;  the cristae of mitochondria swollen and mitochondria membrane damaged and then presented vacuolar mitochondria; the chloroplast deformed, the thylakoids swollen and eventually lead to chloroplasts break. It is concluded that the Cr³⁺ stress with high concentration has an irreversible injury to V. natans leaf cell.