三种观赏植物对重金属镉的耐性与积累特性

通过盆栽实验,对镉(Cd)胁迫下3种观赏植物含羞草、白雪姬和树马齿苋的生长、生理和重金属累积与分布情况进行了研究。结果表明:含羞草、白雪姬和树马齿苋的平均耐性指数分别为105.57、81.35和79.88;在100mg.kg-1Cd浓度下三者叶绿素a、b的含量分别为对照的83.74%、69.83%;60.64%、51.26%和60.64%、51.26%;类胡萝卜素的含量和叶绿素a/b值无明显变化;三者在Cd胁迫下均表现出O2.-离子生成速度上升,MDA含量增加,电导率升高的趋势,其中含羞草的变化幅度最低,白雪姬次之,树马齿苋最高。三者对Cd的耐性表现为含羞草白雪姬树马齿苋。3种观赏植物对Cd均具有较强累积能力,在土壤Cd含量为100mg.kg-1时,三者根和地上部分的Cd累积浓度均高于100mg.kg-1。且对Cd积累能力为树马齿苋含羞草白雪姬。含羞草、白雪姬和树马齿苋在土壤Cd污染的治理中有一定的应用价值。

The characteristics of cadmium tolerance and accumulation in three kinds of ornamental plants

Because of the economical and biological benefits, ornamental plant has become a new source for phytoremediation in recent years. In this study, three kinds of ornamental plants, Mimosa pudica, Tradescantia sillamontana and Porulaca afra were tested under five cadmium ( Cd ) application rate levels that range from 0mg?kg-1 to 100mg?kg-1 by pot-planting method. The growth indexes, physiological indexes and the Cd accumulation in them were studied after a growing period of 50 days. The results showed that Cd had distinct inhibition on the growth of plant, the average tolerance index of M. pudica, T. sillamontana and P. afra were 105.57, 81.35 and 79.88 separately, and the most growth indexes of them had significant differences with the control group in Cd concentration of 50mg?kg-1. The physiological indexes were also influenced by Cd stress obviously, in the content of photosynthetic pigment tested, chlorophyll a contents of M. pudica, T. sillamontana and P. afra were 83.74%, 60.64% and 60.64% separately, compared with the control group, while chlorophyll b contents of them were only 69.83%, 51.26% and 51.26% of the control, but both the contents of carotenoid and chlorophyll a/b values of them were not obviously changed, some of them even raised with the increased Cd concentration, these indicated that Cd do more damage to chlorophyll than to carotenoid, and chlorophyll b was the most sensitive one to Cd pollution in them. For the balance of superoxide system was destroyed under Cd stress, with the rise of Cd, the production rate of superoxide in M. pudica, T. sillamontana and P. afra were all increased, which lead to the accumulation of superoxide and the rise of the MDA contents in three ornamental plants, meanwhile, as a result of the destroyed cell membrane, the selective permeability of cells declined and the electrical conductivity of them were all moved up significantly, the production rate of superoxide, the contents of MDA and electrical conductivity were all correlated well with the Cd added concentration, and the variation range of M. pudica was the smallest, while P. afra was the highest among them. Forming the effects on the growth indexes and physiological indexes, we could found that the tolerance of Cd was M. pudica>T. sillamontana>P. afra. The accumulation and distribution of heavy metals in plant were also important indexes in choosing patient species. In our study, with the rise of the Cd the accumulation of Cd in both the root and the above ground parts of ornamental plants tested were all increased; P. afra had the highest accumulation in them as the Cd concentration in its root and the above ground parts reaching 612.37 mg?kg-1and 259.47 mg?kg-1 separately in 100mg?kg-1, but the transform ability of Cd in T. sillamontana was the strongest under high Cd stress as the translocation factor of it were all above 0.6 from 10mg?kg-1 to 100mg?kg-1. The Cd concentration in these ornamental plants were all above 100mg?kg-1 when the add-concentration of Cd reached 100mg?kg-1 and the accumulation ability was P. afra>M. pudica>T. sillamontana. From the discussion above, we can reach a conclusion that M. pudica, T. sillamontana and P. afra all have high tolerance and strong accumulate ability to Cd, so they all have certain applied value in the treatment of Cd polluted areas.