镧对酸雨胁迫下水稻叶片质膜H+-ATPase活性的影响

为了明晰稀土提高植物抗酸性的内在机制,采用水培法研究了镧(La,15 mg·L~(-1))对酸雨(AR,pH=3.5、2.5)胁迫下水稻叶片质膜H+-ATPase活性的影响.结果显示:与CK相比,pH=3.5 AR组水稻相对生长速率减小,质膜H+-ATPase活性升高,胞内H+增多,CAT活性升高,H_2O_2和MDA含量升高,质膜脂肪酸不饱和度指数(IUFA)降低.La+pH 3.5 AR组水稻各项指标优于pH=3.5 AR组,表明La促使AR下质膜H+-ATPase活性升高,将胞内过多的H+泵出,减缓AR伤害,维持水稻正常生长.另外,La能增强CAT活性,清除过多的H_2O_2,减轻膜脂过氧化程度,使质膜IUFA升高,膜的流动性增强,提高质膜H+-ATPase活性.pH=2.5 AR组水稻相对生长速率、质膜H+-ATPase活性、CAT活性与质膜IUFA均降低,而胞内H+、H_2O_2和MDA含量升高.La+pH 2.5 AR组与pH=2.5 AR组水稻各指标均无明显差异,La对pH=3.5 AR组的缓解效果优于pH=2.5 AR组.综上可知,La对AR下质膜H+-ATPase活性的调节增强了植物耐酸性,这与La能维持AR下较好的质膜环境有关.同时,La的调控效果受AR强度限制.

Effect of lanthanum on plasma membrane H+-ATPase activity in rice leaves under acid rain

To clarify the mechanism of rare earth in improving the resistance of plant to acid rain, the effects of lanthanum (La:15 mg·L^-1) on plasma membrane H⁺-ATPase activity in rice leaves exposed to acid rain (AR:pH 3.5, pH 2.5) by hydroponic in a greenhouse were investigated. The results showed that relative growth rate and index of unsaturated fatty acids in leaves treated with pH 3.5 AR decreased, whereas CAT activity, H₂O₂ content, malondialdehyde content, plasma membrane H⁺-ATPase activity and fluorescence intensity of intracellular H⁺ increased compared with control. All parameters in leaves treated with La+ pH 3.5 AR were superior to those with pH 3.5 AR, indicating that La enhanced the activity of plasma membrane H⁺-ATPase, pumped excess H⁺ out of cells, alleviated the damage caused by acid rain and sustained the growth of stressed plants. On the other hand, La increased the CAT activity, removed the excess H₂O₂, and alleviated lipid peroxidation, leading to the increased index of unsaturated fatty acids and membrane fluidity and enhanced activity of plasma membrane H⁺-ATPase. Moreover, relative growth rate, plasma membrane H⁺-ATPase activity, CAT activity and index of unsaturated fatty acids in leaves treated with pH 2.5 AR decreased whereas fluorescence intensity of intracellular H⁺, H₂O₂ content and malondialdehyde content increased compared with control. However, all parameters in leaves treated with La+ pH 2.5 AR had no significant difference from those treated with pH 2.5 AR. The regulating effects on plants treated with La and pH 3.5 AR was better than those treated with La and pH 2.5 AR. The regulating effects on plants treated with La and pH 3.5 AR was better than that treated with La and pH 2.5 AR. These results implied that La can enhance the adaptation of plants to acid rain by regulating the plasma membrane H⁺-ATPase activity as a result of with favorable membrane environment maintained by La. The regulating effects on plants were dependent on the acidity of acid rain.