| The radionuclides Sr and Cs are the main products of nuclear fission.Their half-life is long,and it is difficult to remove them when they enter into the environment.Long time accumulation will cause radioactive pollution to the soil environment,which is difficult to recover.At present,researchers at domestic and overseas focus on phytoremediation of radionuclide pollution,but there are few reports on biological monitoring of soil radionuclide pollution by plants.In this paper,aiming at the plant monitoring technology of the soil polluted by the nuclides Sr and Cs,and using the higher plants as the research object,the seed sensitivity of the tested plants is preliminarily determined by the seed germination test,and then the plants sensitive to Sr and Cs are selected as the indicator plants of Sr and Cs by the hydroponics method.Finally,by performing the pot experiment,the pollution of Sr and Cs in the soil is simulated,and the indicator effect of plants on Sr and Cs is verified.One step is to explore the effects of Sr and Cs on plant growth morphology and physiological and biochemical aspects.Pearson correlation analysis,factor analysis,and cluster analysis are used to screen plant growth indicators,physiological,biochemical indicators,and plant accumulation indicators to determine the biomarkers of sensitive plants.The main conclusions are as follows:(1)Through the germination test,the sensitivity of seeds to Sr and Cs was judged by the inhibition degree of germination rate and activity index of seeds.The sensitivity of seeds terms of 7 herbaceous plants(Medicago sativa L.,Milk vetch sinicus L.,Lupinus micranthus Guss.,Trifolium repens L.,Poa annua L.,Astilberivularis Buch.-Ham.ex D.Don,Portulaca oleracea L.)to single Sr,single Cs and combined stress(Sr + Cs)was different,which was shown as follows: Sr + Cs treatment > single Cs treatment > single Sr treatment.Compared to control group,the germination rate of the seeds decreased from 70.33% to 13.33%,6.67% and 5.67%,respectively;further,the vigor index of the seeds was decreased by 86.59%,89.68%,and 92.25% compared with the control group.The growth potential of the shoots and roots to the seeds was weak,which was not appropriate to selecte Sr and CS as sensitive indicator plants.(2)The sensitivity of 4 plant species(Milk vetch sinicus L.,Medicago sativa L.,Trifolium repens L.and Lupinus micranthus Guss.to Sr and Cs was evaluated by hydroponics.Under the single Sr treatment,the growth of 4 plant species was promoted to different degrees when the concentration was 0.1 ~ 1.0 mg / L,and when the concentration was 2.0 mg / L,the growth of Trifolium repens L.was inhibited,and the growth of the other 3 plants species had no significant difference with the control.The growth of 4 plant species was as follows: Milk vetch sinicus L.> Lupinus micranthus Guss.> Medicago sativa L.> Trifolium repens L.;when the concentration of single Cs treatment was 0.1 ~ 2.0 mg / L,the growth of Lupinus micranthus Guss.and Medicago sativa L.was less affected.At the concentration of 0.1 mg / L,the growth of Trifolium repens L.was significantly inhibited.At the concentration of 1.0 mg / L,the growth of Milk vetch sinicus L.was inhibited.The growth status of the 4 plant species was as follows: Medicago sativa L.> Lupinus micranthus Guss.> Milk vetch sinicus L.> Trifolium repens L.;under the compound treatment of Sr + Cs,the growth of the 4 plant species was inhibited to varying degrees.When the treatment concentration was 0.1 mg / L,the growth of Trifolium repens L.was significantly inhibited.At the concentration of 1.0 mg / L,the growth of Milk vetch sinicus L.was inhibited.When the concentration was 2.0 mg / L,the growth of Medicago sativa L.and Lupinus micranthus Guss.was inhibited.The growth conditions of 4 plant species were as follows: Medicago sativa L.> Lupinus micranthus Guss.> Trifolium repens L.> Milk vetch sinicus L.;According to the growth conditions of each plant under three treatments and the apparent morphological characteristics of plant leaves,Trifolium repens L.and Milk vetch sinicus L.were selected as Sr and Cs sensitive plants.(3)Under the condition of hydroponics,single Sr treatment had little effect on the growth of 4 plant species,and there was not a large number of leaf chlorosis and yellowing.Under the stress of Cs and Sr + Cs,four kinds of plants all had toxic symptoms,and appeared the phenomenon of leaf yellowing,and the characteristics of leaf yellowing were different.Among them,the leaves of Milk vetch sinicus L.and Trifolium repens L.were the most common.The characteristics of Milk vetch sinicus L.leaf yellowing were water loss and wilting,and gradually lack of green and yellowing.The yellowing characteristics of Trifolium repens L.leaves were obvious and easy to identify,which shown that the yellowing of leaves gradually spreads from the edge to the center of the leaves,until the whole leaves become yellow and dry.With the increase of processing time,the degree of yellowing gradually deepened.Under the soil culture condition,the leaves of Trifolium repens L.and Milk vetch sinicus L.were yellowed more significantly under the treatment of single Sr,single Cs and Sr + Cs at 20 mg / kg,yellowing appeared in different degrees,and the degree of yellowing gradually deepened with the increase of treatment concentration,but the characteristics of yellowing were different from those under hydroponic conditions,the leaves were mostly macular yellowing,which led to plant death in serious cases.Therefore,it was necessary to use the characteristics of leaf yellowing as a sensitive indicator plant biomarker for further study.(4)Under the condition of soil culture,the stress response of plant height to soil Sr and Cs has the effect of time accumulation and dose concentration.After 55 days of plant transplanting,the growth indexes of Milk vetch sinicus L.and Trifolium repens L.decreased gradually with the increase of treatment concentration,which showed that plant height,root length,biomass,leaf number and leaf area per plant were inhibited.When the concentration of single Cs and Sr + Cs was 60 mg / kg and 80 mg / kg,all Trifolium repens L.plants died.When the concentrations of single Sr,single Cs and Sr + Cs were 80 mg / kg,80 mg / kg and 60 mg / kg respectively,all the plants died.With the increase of three concentrations,the physiological level of Trifolium repens L.and Milk vetch sinicus L.clouds showed that the active scavenging system was destroyed,the degree of lipid peroxidation of cell membrane increased,and the content of chlorophyll decreased.The sensitivity of Trifolium repens L.and Milk vetch sinicus L.to Sr and Cs had been confirmed both in plant growth and physiological response.(5)Through the statistical analysis of each index,it was found that under the conditions of hydroponics and soil culture,there was a significant positive correlation between the plant cumulative index and the treatment concentration(the correlation coefficient was greater than 0.8),and the content of Sr and Cs in plants can quantify the degree of Sr and Cs pollution.Under the condition of hydroponics,the aboveground dry weight was more suitable as the biomarker of Trifolium repens L.sensitive to Sr.The rate of yellow leaves per plant,fresh weight and dry weight were more suitable as biomarkers of Cs sensitivity.The yellow leaf rate per plant was more suitable as a biomarker of C s sensitivity.The crown diameter and yellow leaf rate of a single plant were more suitable as biomarkers for the sensitivity of Milk vetch sinicus L.to Sr + Cs compound pollution.The yellow leaf rate per plant was more suitable to be a biomarker sensitive to Sr + Cs compound pollution.In soil culture,the more sensitive the plant was to nuclide pollution,the more serious the plant was under stress.Plant growth related indicators were more suitable for plant sensitive biomarkers,and the yellow leaf rate per plant,dry weight above ground and leaf area per plant were all suitable for plant biomarkers. |
PDF Full Text Request