The Study Of Edta And Plant Growth Regulator Enhance The Remediation Of PB Contaminated Soil By Lolium Perenne

This article studied the effect of EDTA and plant growth regulators, either alone or in combination on Pb uptake efficiency of Lolium perenne, also discussed the role of different treatments in Pb detoxification mechanisms of plant by studing the subcellular distribution and chemical forms of Pb in Lolium perenne. This research prepared external Pb concentrations were0mg kg-1,250mg kg-1,500mg kg-1and750mg kg-1soil, respectively, by adding Pb(NO3)2to the soil.2.5mmol kg-1EDTA was applied to the soil directly. DA-6or GA3, whose concentrations were1μM,10μM and100uM, were sprayed to the leaves. The main results of our research are as follows:(1) The addition of EDTA and/or plant growth regulators all significantly improved the activities of SOD, POD and CAT (P<0.05). Furthermore, apart from the treatment of100μM GA3and/or EDTA, each treatment has decreased the cell membrane permeability and MDA content significantly (P<0.05), and strengthened the resistance of plant, so as to promote the chlorophyll a, chlorophyll b and chlorophyll a/chlorophyll b of Lolium perenne visibility (P<0.05), thus improving the efficiency of plant photosynthesis and plant biomass on the aboveground part;(2)The application of EDTA alone increased the Pb bioaccumulation factor and translocation factor of Lolium perenne by0.8～2.2and0.9～8.3-fold, respectively, as compared to the control, and significantly enhances the Pb enrichment capacity of plant, whereas plant growth was inhibited. The use of DA-6alone or combined with EDTA not only increased shoot biomass of plant by24.0%-96.8%, but also significantly improved Pb concentration of Lolium perenne (P<0.05), with10μM DA-6+EDTA the most effective. Compared to the control, the addition of10μM DA-6along with EDTA increased Pb concentration in root and shoot of Lolium perenne by2.2-3.4and8.0～24.1-fold, respectively, and improved Pb bioaccumulation factor and translocation factor to3.2-4.1and0.23-1.12, respectively, moreover, Pb extraction amount of per plant and extraction efficiency reached to2.3μg～176.5μg and0.65%～2.2%, respectively1μM or10μM GA3alone or incombination with EDTA increased acrial part biomass and Pb concentration of Lolium perenne by9.2%～62.5%and15.0%～323.1%, respectively, as compared to the control, in addition, Pb bioaccumulation factor and translocation factor were significantly enhanced (P<0.05), and improved Pb extraction amount of per plant and extraction efficiency by0.4～12.8and0.5～14.5-fold, respectively, among which1μM GA3+EDTA was the most significant. Under the treatment of1μM GA3+EDTA, the shoot and root Pb content were increased by1.6～3.8and5.6～14.8-fold, respectively, as compared to the control. On the contrary, foliar spray100μM GA3significantly suppressed the growth and Pb enrichment of Lolium perenne (P<0.05). Although the application of100μM GA3+EDTA decreased the biomass of plant, the shoot and root Pb content of Lolium perenne were increased by18.2%～124.8%and151.7%-415.4%, respectively, thereby increasing Pb extraction amount of per plant and extraction efficiency by0.8～3.4and0.9～2.5-fold, as compared to the control.Under the condition of this experiment, the strengthening effect of10μM DA-6+EDTA on Lolium perenne repair Pb contaminated soil was superior to the addition of1uM GA3+EDTA, indicating the application of10μM DA-6combined with EDTA was more suitable to enhance the efficiency of Lolium perenne remediation of heavy metal contaminated soil;(3) The research of Pb subcellular distribution in shoot of Lolium perenne shows that:Pb fixation by cell wall and compartmentalization by vacuole play important roles in Pb detoxification of plant shoot. Foliar spray DA-6or (1μM or10μM) GA3facilitated the cell wall deposition and vacuole compartmentalization, and significantly reduced Pb concentration in organelles components, thus relieving the damage of plants, consequently, significantly improved the biomass of Lolium perenne (P<.05). In contrast, the treatment of100μM GA3and/or EDTA significantly increased Pb concentration in organelles components, and heightened the Pb hazard on plant, as a result of inhibition plant growth (P<.05);(4)The study of Pb chemical forms in Lolium perenne shoot suggests:a majority of Pb was associated with pectates and proteins (FNaCl), followed by heavy metal-phosphate complexes (FHAc). Among different chemical forms, FE, FW and FNaci are remarkably stronger migration ability than that of other chemical forms of Pb, and be more toxic to plant. Foliar spray DA-6or1μM GA3decreased the mobility of Pb and hence, alleviated Pb damage to the Lolium perenne; Under the treatments of DA-6or (1μM or10μM) GA3along with EDTA, Pb propotions on FE, FW and FNaci was increased, but still lower than EDTA treatment alone, indicating that foliar spray DA-6or (1μM or10μM) GA3can relieve the hazard of EDTA and/or Pb on Lolium perenne, thereby significantly increased plant biomass (P<0.05). The addition of100μM GA3alone or in combination with EDTA remarkablely increased Pb removability in plant, thus significantly inhibited plant growth (P<0.05).