铬胁迫对芥菜型油菜生理特性和铬富集的影响

Effects of Cr (Ⅵ) Stress on Physiological Characteristics of Brassica juncea and Its Cr Uptake

采用盆栽试验研究了重金属铬胁迫对芥菜型油菜来凤芥菜和四川黄籽的出苗率、幼苗生物量、叶绿素含量、丙二醛含量(MDA),超氧化物歧化酶(SOD)、过氧化物酶(POD)活性、铬的亚细胞分布和铬富集的影响.目的是为阐明植物遭受铬胁迫的毒害机制和铬污染土壤的植物修复提供理论依据.结果表明,低浓度铬能够促进芥菜型油菜生长,提高出苗率,增加幼苗生物量和叶绿素含量,但MDA含量降低;高浓度铬导致芥菜型油菜出苗率、幼苗生物量和叶绿素含量下降,MDA含量增加,并且MDA含量与叶绿素含量呈显著负相关.当土壤中外源铬浓度<300 mg/kg时,铬处理导致2种油菜叶片中SOD和POD活性都增加,但是当铬浓度>300 mg/kg时,铬抑制叶片中SOD和POD活性.来凤芥菜和四川黄籽叶片富集的铬主要分布于细胞质中(分别为48.57%～64.77%和41.03%～76.42%),其次为细胞壁,而叶绿体和线粒体中含量很低(<10%).相对而言,四川黄籽能够耐受较高浓度的铬胁迫.2种油菜根和地上部分铬含量随铬处理水平的提高而增加.在加入300 mg/kg铬的土壤中,芥菜型油菜生长70 d后,来凤芥菜和四川黄籽叶片累积铬的平均浓度分别达167.30和197.60 mg/kg,平均每株地上部富集铬总量均达最大值,分别为1.71和2.81 mg/plant,平均每株从土壤中带走的铬分别占土壤中全铬含量的0.23%和0.38%.在铬污染土壤植物修复中,四川黄籽具有潜在的应用价值.

In order to identify the toxic mechanism of plant under chromium（Cr） stress,provide theoretic foundation for phytoremediation of Cr-contaminated soil,pot experiment was conducted to investigate the effects of heavy metal Chromiumstress on the emergence rate,the biomass of seedlings,the contents of chlorophyll,malonyldialdehyde（MDA）,the activities of superoxide dismutase（SOD）,peroxide enzyme（POD）,Cr subcellular distribution in the leaves and Cr uptake in Brassica juncea.The results indicated that the emergence rate of seedlings,the biomass and the chlorophyll content of B.juncea were increased under lower Cr（Ⅵ） concentrations.However,lower emergence rate,biomass and chlorophyll content were observed for the higher Cr（Ⅵ） concentrations.The content of malonyldialdehyde（MDA） was reverse with increased Cr（Ⅵ） concentration,and there was significantly negative correlation between MDA and Chlorophyll content.The activities of SOD and POD were increased under 300 mg/kg Cr（Ⅵ）,but the activities of SOD and POD were decreased above 300 mg/kg Cr（Ⅵ）.Cr was mainly distributed in the cytoplasm of leaves（48.57%-64.77%,41.03%-76.42%,respectively）and the second in the cell wall,and less distributed in the mitochondrion and chloroplast（10%） in Laifengjiecai and Sichuanhuangzi.Sichuanhuangzi could accumulate more Cr in leaves than Laifengjiecai from the Cr-contaminated soil.As compared to Laifengjiecai,Sichuanhuangzi has stronger tolerance to Cr（Ⅵ） pollution.The Cr contents in stem,leaf and root of B.juncea usually were heightened with increased concentrations of Cr（Ⅵ） in soil.Average Cr concentration in the leaves of Laifengjiecai and Sichuanhuangzi were167.30 and 197.60 mg/kg,respectively for 70 days growing in the soil spiked with 300 mg/kg Cr（Ⅵ）,the maximum of Cr content in plant shoots were 1.71 and 2.81mg/plant,respectively,namely,Cr removed by plant shoots were 0.23% and 0.38% of Cr content in treated soil,respectively.The results suggest that Sichuanhuangzi is promising for the phytoremediation of Cr-contaminated soil.