Abstract: In order to explore the possible physiological mechanisms of calcium involved in improving adaptation to nickel stress in plants,the effects of external calcium(Ca2+)on the activities of superoxide dismutase(SOD),catalase(CAT),peroxidase(POD)and ascorbate peroxidase(APX),the contents of H2O2 and malondialdehyde(MDA),and electrolyte leakage of leaf tissues were investigated in nickel-stressed rice seedlings.Under 0.1 mmol/L nickel(Ni2+)treatment,the activities of SOD,CAT and APX in rice leaf tissues were significantly decreased,while the activity of POD was obviously enhanced.Moreover,nickel treatments significantly increased the contents of H2O2 and MDA in rice leaf tissues,suggesting oxidative damage and membrane peroxidation occurred in nickel-treated leaf tissues.External calcium promoted the activities of SOD,CAT,APX and POD,but reduced considerably H2O2 and MDA contents and permeability of cell membrane in leaf tissues during the stress period.In addition,the activities of CAT,SOD,POD and APX in 10 mmol/L Ca2+-supplemented leaf tissues were higher,and H2O2 and MDA contents were lesser than those in 5 mmol/L Ca2+ under the nickel stress.It was suggested that one of the mechanisms that external calcium enhanced the tolerance to nickel toxicity in rice seedlings was mediated by improving scavenging of active oxygen species and maintaining the integrity of cell membrane under nickel stress.

Key words: nickel toxicity, calcium, antioxidant enzyme, active oxygen species, membrane lipid peroxidation, rice

摘要： 研究了外源钙（Ca2+）对镍胁迫下水稻叶片组织超氧化物歧化酶（SOD）、过氧化氢酶（CAT）、过氧化物酶（POD）和抗坏血酸过氧化物酶（APX）的活性、H2O2和丙二醛（MDA）含量以及质膜电解质渗透的影响，以探讨钙缓解植物镍毒性的生理机制。0.1 mmol/L镍（Ni2+）胁迫下水稻叶片组织SOD、CAT和APX活性明显下降，POD活性明显上升，H2O2和MDA含量、电解质渗漏率显著增大，说明镍诱导了细胞发生明显的氧化损伤和膜脂过氧化；钙提高了镍胁迫下叶片组织中SOD、CAT、POD和APX活性，显著降低了H2O2、MDA含量和电解质渗漏率，且10 mmol/L Ca2+处理的抗氧化酶活性上升的程度和H2O2、MDA含量和电解质渗漏率下降的程度比5 mmol/L Ca2+处理的大。提示钙通过促进镍胁迫下水稻叶片组织抗氧化酶活性，增强活性氧清除能力，维持细胞膜结构的稳定，是钙减轻镍对水稻毒性的生理机制之一。

关键词: 镍毒性, 钙, 抗氧化酶, 活性氧, 膜脂过氧化, 水稻