Tolerance Mechanism And Accumulation Characteristic Of Polygonum Runcinatum Under Cadmium, Lead And Zinc Stress

Phytoremediation of heavy metal polluting soil is an important way to make soil contaminant nontoxic. Screening hyperaccumulator is the core and basis of phytoremediation. So research on tolerance and accumulation characteristics of plants under heavy metal pollution of soil has become a hotspot home and abroad. On the basis of field investigation, the Polygonum runcinatum has been selected to research the tolerance mechanism and accumulation characteristic under Cadmium (Cd),Lead (Pb) and Zinc (Zn) stress, which was studied based on the pot culture experiment. The main results were as follows:(1) Polygonum runcinatum could grow normally in wild condition. They had great tolerance to Cd, Pb and Zn, and they had great ability of accumulation to Cd and Zn. The average Cd, Pb and Zn concentrations of Polygonum runcinatum were16.65mg kg-1、9.87mg kg-1and326.65mg kg-1, respectively. Their bioconcentration factors (BCF) were1.01、0.03and2.96, and their transport coefficients (TF) were1.36、0.05and1.81, respectively. Therefore, the BCFs and TFs of Cd and Zn were greater than one. Moreover, the maximum Cd, Pb and Zn accumulation of Polygonum runcinatum were1688.07μg、364.11μg and43602.51μg, respectively.(2) Polygonum runcinatum showed very strong tolerance and accumulation abilities under Cd stress. When the treatment concentration of Cd<120mg kg-1, Cd had effects on facilitating the shoot growth, that the plant height and shoot biomass were more than the control (CK). However, when the treatment concentration of Cd>120mg kg-1, the growth of Polygonum runcinatum started to be inhibited, the plant height and shoot biomass were less than CK. With the increasing of treatment concentration, the photosynthetic characteristics, CAT, POD activities and GSH contents had a tendency that increasing firstly and then decreasing. While the treatment concentration of Cd was150mg kg-1, the Cd concentration of Polygonum runcinatum was117.24mg kg-1which had reached the standard for the the Cd concentration of the hyperaccumulator (Cd>100mg kg-1). Polygonum runcinatum took up Cd from the soil and distributed large amounts of it to the shoot. The accumulation of shoot accounted for82.06%of the whole plant, and the accumulation of shoot was4.57times than the root. Furthermore, the BCF (1.32-6.85) and TF (2.48～9.01) of Polygonum runcinatum at all levels were more than 1, which had reached the standard for the the Cd concentration of the hyperaccumulator (BCF, TF>1).So Polygonum runcinatum had strong ability of the tolerance and accumulation.(3) Polygonum runcinatum showed strong tolerance under Pb stress. The biomasses of Polygonum runcinatum under all levels were more than CK. The biomass was significantly higher than CK, while the concentration of Pb was1800mg kg-1(P<0.05). With the increasing of treatment concentration, the CAT and POD activities had a tendency which increasing firstly and then decreasing. The Pb concentration of roots, stems and leaves increased with the increasing of the Pb treatment concentration. While Pb was1800mg kg-1, they reached the highest Pb concentration that were1312.60mg kg-1、67.65mg kg-1and43.49mg kg-1, respectively. However, the highest Pb concentration of shoot was55.57mg kg-1, which was less than the standard for the Pb concentration of the hyperaccumulator (1000mg kg-1). Moreover, the BCF and TF of Polygonum runcinatumat at the levels (Pb<100mg kg-1) were significantly lower than at other levels (P<0.05), and its BCF and TF hadn’t reached the standard for the the Pb concentration of the hyperaccumulator (BCF, TF>1).So Polygonum runcinatumat showed strong tolerance but puny accumulation under Pb stress.(4) Polygonum runcinatum showed strong tolerance and accumulation abilities under Zn stress. When the treatment concentration of Zn<2500mg kg-1, the biomass, root length and plant height were higher than CK. With the increasing of treatment concentration, the CAT and POD activities had a increasing tendency, and they were higher than CK. The highest concentration of root was1288.25mg kg-1, while the treatment concentration of Zn was3000mg kg-1. The highest concentration of stem and leave were723.21mg kg-1and1393.88mg kg-1, when the treatment concentration of Zn was2500mg kg-1. Furthermore, when the treatment concentration of Zn was2500mg kg-1, the TF (1.60) of Polygonum runcinatumat was significantly higher than others (P<0.05), and also reached the standard for the Zn concentration of the hyperaccumulator (TF>1)...