大白菜叶片表皮毛特征及重金属镉砷的累积特性

Characteristics of trichome and the accumulation of cadmium and arsenic in leaves of Chinese cabbage

针对大白菜镉、砷等重金属累积及分布特性可能与叶片表皮毛形成有关的问题,以叶片有表皮毛的3个大白菜基因型(野生型A03,突变体lcc-1,268)和叶面光滑无表皮毛的1个基因型(CC48)为试验材料,通过盆栽方法将其种植在重金属镉(Cd)、砷(As)复合污染土壤中,探究3个大白菜基因型叶片表皮毛的外观特征,以及采用扫描电镜-能谱的方法表征镉、砷在表皮毛基部的分布状况,最终诠释镉砷在大白菜叶片的累积特性。结果表明,大白菜野生型A03和突变体lcc-1的表皮毛在整个叶片上下表皮均有分布,且前者叶片边缘表皮毛数量显著高于后者的,而268基因型大白菜叶片下表皮的表皮毛主要在叶脉上,且随着叶龄增加而逐渐减少;扫描电镜观测结果显示3种基因型大白菜的表皮毛全貌非常相似,均为圆锥状,无分枝,基部宽,末端渐尖。结合电子探针进行表皮毛镉、砷的微区定位能谱扫描分析,发现As、Cd在野生型和突变体的表皮毛广泛分布,在基部中分别达0.1%、0.03%和0.09%、0.24%。电感耦合等离子体质谱(ICP-MS)分析表明有表皮毛的大白菜基因型A03、突变体lcc-1和268的老叶对Cd、As的富集能力显著大于没有表皮毛的基因型CC48,分别为4.7、8.9倍,1.9、4.7倍,1.9、3.6倍。总之,野生型A03表皮毛数量较多,同时有表皮毛的大白菜新叶和老叶对镉、砷的富集能力均较强,说明表皮毛对镉砷的区隔化是大白菜解毒的作用机制之一。

The accumulation and distribution characteristics of cadmium and arsenic in Chinese cabbage might be related to the formation of trichome.A soil pot experiment was conducted to explore the characteristics of trichomes and the accumulation of cadmium and arsenic in leaves via SEM-EDX and ICP-MS on 3 varieties with trichome and 1 variety without trichome that were planted in Cd/As contaminated soil.The results showed that the trichomes mainly grew on the adaxial and abaxial epidermis of A03 and lcc-1,and numbers of trichomes along the leaf margin of A03 were significantly higher than those of lcc-1.However,trichome mainly distributed in the veins of abaxial epidermis of variety 268,whose trichome number decreased gradually with leaf age.The trichome shape of the three varieties was similarity under SEM that were conical shape without branches.Moreover,Cd and As accumulated on trichome in common and the contents of As and Cd at the base of trichome were 0.1%,0.03%and 0.09%,0.24%examined by SEM-EDX.The accumulation of As and Cd in old leaves of A03,lcc-1 and 268 with trichome were 8.9 folds,4.7 folds,3.6 folds of that of trichomeless mutant via ICP-MS,respectively.In summary,wild type A03 with more trichome could accumulate more As and Cd,which indicated that compartmentalization of As and Cd by trichome is one pathway for detoxicity of Chinese cabbage.