Tolerance And Accumulation Characteristics Of Nicandra Physalodes L. Under Cadmium, Lead And Zinc Stress

According to a field survey and a pot experiment, we studied the tolerance and accumulation characteristics of Nicandra physalodes L. taken from a lead-zinc mine area in Hanyuan, Sichuan, China under three single pollution of Cd, Pb. Zn. A plot experiment was conducted to study the ability of N. physalodes for phytoremediation to the Cd, Pb, Zn polluted soils. The main results showed as follows:(1) N. physalodes had a stong tolerance and accumulation characteristics of CdUnder field conditions the plants grew normally. When the soil Cd concentrations≤90mg kg-1, there were no statistically significant differences in plant height, root length and dry weight between control and treated plants (P＞0.05), even at the low soil Cd concentrations, the growth was stimulated. Chlorophyll concentrations in N. physalodes were barely affected by the treatments(P＞0.05), the photosynthetic system was not obviously harmed. The activities of POD, SOD and CAT in leaves and roots increased in the present study to different extents. Antioxidant enzymes have been shown to work in a cooperative or synergistic way to protect against oxidative stress. Cd concentrations in roots exceeded100mg kg-1when the soil Cd concentration was≥10mg kg-1. Cd concentrations in shoots exceeded100mg kg-1when the soil Cd concentration was≥60mg kg-1and reached a maximum of214.47mg kg-1for the180mg kg-1rate. Shoot accumulation of Cd reached a maximum of4.08mg pot-1at the soil Cd concentration of60mg kg-1with shoots absorbing1.13%of the Cd added to the pot. BCF values of N. physalodes shoots and roots were all greater than1, with maximum values of7.04for shoots and16.30for roots. No values of TF exceed1. Although it could not be classified as a Cd hyperaccumulator, N. physalodes have a much greater shoot than root biomass, considerable Cd would be extracted when they were harvested. Thus this plant has great potential to be used for phytoremediation of contaminated soils by Cd.(2) N. physalodes had strong tolerance and some accumulation ability of PbUnder field conditions and the pot experiment, the plants grew normally. There were no statistically significant differences in plant height, root length and dry weight between control and treated plants (P＞0.05). Chlorophyll concentrations in N. physalodes were barely affected by the treatments(P＞0.05). When the soil Pb concentration was600mg kg-1, the activities of POD in leaves and roots reached the largest, then didn’t change obviously. The activities of CAT in roots had no statistically significant differences(P＞0.05), and fistly increased and then decreased in leaves. With increasing rates of added Pb, Pb concentrations in roots and shoots increased. Pb concentrations in roots were highly significantly affected by soil Pb concentrations (P＜0.001) as shown by the linear correlation. Pb concentrations in shoots were highly significantly affected by soil Pb concentrations (P＜0.001) as shown by the quadratic relationship(P＜0.001). With increasing rates of added Pb, Pb accumulations in roots and shoots increased. The values of BCF and TF didn’t exceed one. So N. physalodes had some accumulation ability of Pb.(3) N. physalodes had strong tolerance and some accumulation ability of ZnIn pot experiment, plant height, root length were significantly greater than the control or were no statistically significant differences except when soil Zn concentrations is5000mg kg-1. When soil Zn concentrations≥4000mg kg-1, the biomass was negatively affected under the zinc stress. Chlorophyll concentrations in N. physalodes were barely affected by the treatments(P＞0.05). With increasing rates of added Zn, the activities of POD and CAT in roots increased. The activities of POD in leaves were no statistically significant differences between treatments (P＞0.05). The activities of CAT in leaves were fistly increased and then decreased. With increasing rates of added Zn, Zn concentrations in roots and shoots increased. Zn concentrations in roots and shoots were highly significantly affected by soil Pb concentrations (P＜0.001) as shown by the linear correlation. Zn accumulations in shoots were highly significantly affected by soil Pb concentrations (P＜0.001) as shown by the quadratic relationship(P＜0.001), and took the the vast majority of the total plant Zn uptake. The values of BCF of shoots and roots were0.50-4.23and0.31-1.97respectively and the values of TF were0.47-0.64. N. physalodes had some accumulation ability of Zn.(4) N. physalodes had great potential phytoremediation capability in Cd polluted soils, and had some accumulation ability in Pb or Zn polluted soils In the plot experiment, the plants grew well. The plants can be harvested2096.90kg/hm2. The largest Cd concentrations in shoots was up to103.55mg kg-1. Roots and shoots can take13.97g/hm2å'Œ94.61g/hm" cadmium from the polluted soil. The mean values of BCF of shoots and roots exceed two. The translocation factors of57.14%plants exceed one. As a Cd accumulator. N. physalodes is a potential plant material for phytoremediation. Meanwhile, N. physalodes had some accumulation ability in Pb or Zn polluted soils, the accumulation of lead and zinc in shoots were50.95g/hm2and460.72g/hm2respectively.