烟草对镉的吸收积累特性及镉的化学形态分布

Characteristics of absorption,accumulation and chemical speciation of Cd in tobacco

为明确烟草对重金属镉(Cd)的吸收积累特性及其化学形态分布特点,采用水培试验研究了烟草对Cd的吸收特性,以及在不同Cd浓度下烟草根茎叶Cd含量(质量分数)及其化学形态分布。结果表明,烟草对Cd的吸收量随着Cd处理时间的推移呈现先降低后升高的趋势,达到240μg·株^(-1)时趋于稳定,之后又有所降低。烟草对Cd的吸收速率则呈现高-低-高的变化趋势,烟草移栽入含Cd培养液中4~5 h时,对Cd吸收速率最高。随着Cd处理浓度的增加,烟草干物质的积累量先升高后降低,低浓度Cd处理的烟草干物质量增加。不同Cd浓度处理,烟草不同部位Cd含量排序依次为茎>根>叶,且随着Cd浓度的增加各部位的Cd含量均增加。烟草根系中Cd以去离子水提取态为主,其次为醋酸提取态,叶片中Cd主要以醋酸结合态存在。Cd处理浓度提高时,烟草中Cd由活性弱的化学形态向活性强的形态转化。

To clarify the characteristics of absorption,accumulation and chemical speciation of cadmium（Cd） in tobacco,the Cd absorption characteristics in tobacco,the contents and chemical speciation of Cd in tobacco roots,stalks and leaves at different Cd concentrations were studied by hydroponic experiments.The results showed that the amount of Cd absorption in tobacco decreased first then increased with the proceeding of Cd treatment;it became stable at 240 μg·plant-1then decreased after that.The Cd absorption rate of tobacco presented a tendency of increase-decrease-increase and peaked within 4-5 hours after tobacco plants were transplanted in Cd solutions.With the increase of Cd concentration,the accumulation of dry matter in tobacco increased first and then decreased,and the dry matter weight was raised at a low Cd concentration.At different Cd concentrations,Cd content was the highest in stalks and the lowest in leaves,and it increased in all parts of tobacco with the increase of Cd concentration.The Cd in roots was mainly deionized water-extractable Cd,followed by acetic acid-extractable Cd,the Cd in leaves mainly existed in the form of binding to acetic acid.With the increase of Cd concentration,the Cd chemical speciation transformed from low activities in tobacco into the chemical speciation with high activities.