一株Cr(Ⅵ)还原菌对Cr(Ⅵ)胁迫下小白菜幼苗植物毒性及植物有效性的缓解效应

Mitigative Effects of a Cr(Ⅵ)Reducing Bacterium on Plant Phytotoxicity and Phytoavailability of Pakchoi Seedlings under Cr(Ⅵ)Stress

【目的】研究Cr(Ⅵ)还原菌Exiguobacterium sp.EH5(简称菌株E)对Cr(Ⅵ)胁迫下四季青小白菜幼苗的植物毒性及植物有效性的影响。【方法】通过水培盆栽试验,向等体积、含有不同Cr(Ⅵ)质量浓度(0、1、2、3、4、5 mg/L)的水培营养液中按体积比1%添加菌悬液(菌悬液OD600nm≈4),考察菌株E对Cr(Ⅵ)胁迫下小白菜幼苗的生长量、叶绿素含量、蛋白质含量、丙二醛(MDA)含量、超氧化歧化酶(SOD)活性及铬含量的影响。【结果】(1)Cr(Ⅵ)质量浓度越高,Cr(Ⅵ)毒性抑制小白菜幼苗生长及其蛋白质、叶绿素合成的效果越显著。加入菌株E后,在相同最高Cr(Ⅵ)质量浓度(5 mg/L)对比下,小白菜幼苗茎长、根长、鲜重、叶绿素总量及蛋白质含量比不加菌E对照分别增加98.10%、5.32%、90.49%、10.07%、11.11%。(2)随着Cr(Ⅵ)胁迫质量浓度升高,小白菜幼苗叶片中MDA含量增加,SOD活性随着Cr(Ⅵ)质量浓度升高呈先增后降趋势。加入菌株E后,在相同质量浓度1~5 mg/L下,小白菜幼苗叶片中MDA含量比不加菌对照分别降低19.60%、17.05%、58.85%、28.19%、11.66%。在Cr(Ⅵ)胁迫质量浓度≤4 mg/L时,加菌株E的SOD活性比不加菌对照有所降低,随着Cr(Ⅵ)质量浓度升高(>4 mg/L),加菌株E的SOD活性比不加菌对照提高11.51%。(3)Cr(Ⅵ)胁迫质量浓度越高,小白菜幼苗体内(根、茎叶)Cr含量越高。加入菌株E后,小白菜幼苗根、茎叶部分的Cr含量比不加菌对照均有不同程度的降低。【结论】添加菌株E可以在一定程度上缓解Cr(Ⅵ)对小白菜幼苗的生长毒性以及Cr(Ⅵ)诱导的氧化胁迫,并降低小白菜幼苗对Cr(Ⅵ)的可利用度。

【Objective】This paper is to study the effects of a Cr(Ⅵ)reducing strain Exiguobacterium sp.EH5(hereinafter called strain E)on the phytotoxicity and phytoavailability of Pakchio seedlings under Cr(Ⅵ)stress【.Method】The effects of strain E on the growth and concentrations of chlorophyll,protein,malondialdehyde(MDA),superoxide dismutase(SOD)and chromium in Pakchio seedlings under Cr(Ⅵ)stress were investigated by pot culture experiment,in which the bacterial suspension with a volume ratio of 1%(bacterial suspension OD600 nm≈4)was added into the hydroponic nutrient solution.【Result】(1)Under the experimental conditions,when the concentration of Cr(Ⅵ)was higher,the Cr(Ⅵ)toxicity showed greater inhibition effects on the growth of Pakchio seedlings and their protein and chlorophyll synthesis.After adding strain E,at the same maximum concentration of Cr(Ⅵ)(5 mg/L),compared with the group without adding strain E,the stem length,root length,fresh weight,total chlorophyll and protein content of Pakchioi seedlings increased by 98.10%,5.32%,90.49%,10.07%and 11.11%,respectively;(2)With concentration increasing of Cr(Ⅵ)stress,the MDA content in the leaves of Pakchoi seedlings increased,the SOD activity was ascend in first and descend at last with concentration of Cr(Ⅵ)increasing.After adding strain E,at the same concentration of 1-5 mg/L,the MDA content in leaves of Pakchoi seedlings decreased by 19.60%,17.05%,58.85%,28.19%and 11.66%,respectively,compared with that in group E without adding strain E.When the concentration of Cr(Ⅵ)stress was≤4 mg/L,the activity of SOD enzyme in the inoculated group decreased compared with that in the non-inoculated group under the same concentration.Then,with the increase of concentration of Cr(Ⅵ)(>4 mg/L),SOD activity in the group with strain E was 11.51%higher than that in the non-added group.(3)The Cr content in the roots,stems and leaves of Pakchoi seedlings was higher with the increase of concentration of Cr(Ⅵ)stress.After adding strain E,Cr content in the roots,stems and leaves of Pakchoi seedlings decreased compared with that in the group without strain E.【Conclusion】The addition of strain E could alleviate the growth inhibition and oxidative stress from Cr(Ⅵ)on Pakchoi seedlings by reducing the bioavailability of Cr(Ⅵ)by Pakchoi seedlings.