湿地植物水蓼(Polygonum hydropiper L.)对镉的富集特征及生理响应

Accumulation Characteristics and Physiological Responses of the Wetland Plant,Polygonum hydropiper L.to Cadmium

以人工湿地修复镉污染水体时,植物在镉离子的沉淀、吸收和积累等过程中起着关键作用,但当前报道的镉富集植物种类较少,湿地植物对镉胁迫的生长及生理响应缺乏系统研究,限制了湿地植物在镉污染水体修复中的应用。笔者以常见湿地植物水蓼(Polygonum hydropiper L.)为对象,设置了4个镉处理浓度(0、0.5、1和2 mg·L^-1),研究了水蓼对镉的富集特征以及生长和生理响应。水蓼根、茎和叶的镉含量(以干重计)随镉处理浓度的增加而升高,处理30 d时,在2 mg·L^-1处理下分别达到134、47和48 mg·kg^-1。处理30 d时,在1 mg·L^-1的镉处理下,水蓼的地上部及地下部富集系数和转运系数最高,地上部和地下部富集系数分别为45.6和111.7,转运系数为0.41。在处理15 d时,水蓼生物量、叶绿素含量和超氧化物歧化酶(SOD)活性在2 mg·L^-1处理下显著降低。在处理30 d时,水蓼的总生物量在不同镉浓度下无显著差异,但丙二醛(MDA)含量、SOD和过氧化氢酶(CAT)活性在0.5~2 mg·L^-1镉处理下均显著升高,叶绿素含量下降。这些结果表明,水蓼可以通过提高抗氧化酶活性等机理抵抗镉胁迫产生的氧化伤害,并且水蓼对镉的富集和转运系数较高,具有在镉污染水体修复中应用的潜力。

In the remediation of constructed wetland for cadmium-contaminated water,the plant plays a key role in the precipitation,absorption and accumulation of cadmium ions.However,due to the lack of the species of cadmium-enriched plants,the growth and physiological responses of wetland plants to cadmium stress were not studied systematically,leading to the limited application of wetland plants in the restoration of water-body polluted by cadmium.We choose Polygonum hydropiper L.,a common wetland plant,as the target plant,and study the character-istics of cadmium accumulation,and the growth and physiological responses,with four cadmium concentrations(0,0.5,1 and 2 mg·L^-1).As the cadmium concentration increased,the cadmium contents(based on dry weight)in the roots,stems and leaves increased,being 134,47 and 48 mg·kg^-1 at 2 mg·L^-1 concentration after 30 d treatment.The bioconcentration factor(BCF)and translocation factor(TF)were the highest under 1 mg·L^-1 concentration after 30 d treatment,where BCF of the shoot and root were 45.6 and 111.7 respectively,and TF was 0.41.At 2 mg·L^-1 cadmium concentration,the biomass,chlorophyll content and superoxide dismutase(SOD)activity decreased dramatically after 15 d treatment.After 30 d treatment,there was no significant difference in total biomass of Polygonum hydropiper L.,but remarkable increase was observed in the malondialdehyde(MDA)content,and the activities of SOD and catalase(CAT),whereas the chlorophyll content declined at 0.5~2 mg·L^-1 cadmium concentration.It is indicate that Polygonum hydropiper L.can resist the oxidative damage caused by cadmium stress with the improvement of the activities of antioxidant enzymes.Both BCF and TF of cadmium in Polygonum hydropiper L.are high,so it is fair to conclude that Polygonum hydropiper L.possesses high application potentiali-ty in the remediation of cadmium-contaminated water.