Effects of different Ni concentrations on the accumulation of Ni and nutrient elements, oxidative stress and antioxidant system in <i>Hydrocharis dubia</i> leaves

Abstract

采用营养液水培的方法,研究不同镍(Ni)添加浓度(0、0.05、0.10、0.15、0.20 mmol/L)对水鳖(Hydrocharis dubia)叶片中Ni元素积累、营养元素(Ca、Mg、K、Fe和Mn)含量、氧化胁迫和抗氧化系统的影响.结果显示:(1)叶片中Ni含量以浓度依赖的方式增加;(2)叶片中营养元素含量(Ca、Mg、K、Fe、Mn)也受影响,其中Ca、Mg含量随Ni浓度增加而显著上升;K含量随Ni浓度增加有所升高,但不显著;Mn含量虽在较大Ni浓度时有所下降,但处理组始终高于对照组;而Fe含量则随Ni浓度增加而下降;(3)Ni胁迫诱导了明显的氧化胁迫,主要表现为:O₂^·-产生速率以及过氧化氢和丙二醛含量显著升高,可溶性蛋白以及光合色素含量明显下降;(4)随着Ni浓度的升高,过氧化物酶活性逐渐升高,过氧化氢酶活性呈下降趋势,超氧化物歧化酶活性在Ni添加浓度为0.05 mmol/L时出现短暂升高随后下降;维生素E和黄酮含量随Ni浓度增加呈缓慢上升趋势;还原型谷胱甘肽未发生明显变化,非蛋白巯基和植物络合素含量均表现为先升后降的趋势;总抗氧化能力随Ni浓度升高先增强后减弱.由此可见,Ni添加引起水鳖叶片中Ni元素的累积和营养元素含量变化,同时产生明显的氧化胁迫,打破了抗氧化系统的平衡.;This article adopts the method of hydroponic nutrient to study the effects of Ni concentrations added in different experiments(0, 0.05, 0.10, 0.15 and 0.20 mmol/L)on the Ni and nutrient elements contents, oxidative stress and antioxidant system in Hydrocharis dubia leaves. The results indicated that:(1)Ni content in leaves increases with the Ni concentration in solution.(2)Nutrient elements(Ca, Mg, K, Fe and Mn) in leaves are also affected by the solution. The content in Ca and Mg increases significantly with the increase of Ni concentration in solution. The content of K increases, but not significantly in leaves. Though Mn content of leaves decreases in the solution with higher Ni concentration, the treatment groups contain generally Mn in leaves higher than the control group. However, Fe content in leaves declines with the increasing of Ni concentration in solution.(3)Ni stress induces the apparent oxidative stress, characteristic of the increases of the productive rate of O₂^·- and the contents of H₂O₂ and MDA, and the obvious decreases of the contents of soluble protein and photosynthetic pigment in leaves.(4)With the increase of Ni concentration in solution, the activity of peroxidase in leaves increases gradually, while the activity of catalase is declined, followed by the firstly increasing and then decreasing activity of superoxide dismutase at 0.05 mmol/L in leaves. The content of vitamin E and flavonoids in leaves rises slowly with the increasing of Ni concentration in leaves. No apparent change of the glutathione is observed. The content of non-protein thiol and plant complexation both show increases at first. Total antioxidant capacity enhances firstly with Ni concentration in solution. Thus it can be seen that Ni stress causes the accumulation of Ni and the variation of nutrient elements in Hydrocharis dubia leaves, and generates obvious oxidative stress, breaking the balance of antioxidant system.