| At present,heavy metal pollution is becoming more and more serious,and its negative effects on biodiversity and stability of natural ecosystems has attracted growing attentions.This study was to investigate the effects of heavy metal with different pollution duration(compared between plant matters with long-term pollution experience or without pollution)on plant population structure and ecological responses.We chosen Datura str amonium that was experienced with different background of heavy metal pollution(in which the populations persistently grew in high concentration of heavy metal contamination called MP1 and MP2;and the population grew without heavy metal contamination called NMP1 and NMP2),as experimental materials and cultivated under three kinds of heavy metal pollution(Pb1000 mg/kg,Cd30 mg/kg and Pb1000 mg/kg +Cd30 mg/kg)to simulate heavy metal pollution conditions.Then,quantitative characteristics,resources allocation and molecular ecological characteristics were obtained to analyse the mechanism of pollution-experience on plants acclimation to heavy metal contamination.The results were showed as follows:(1)The change of quantitative characteristics of Datura stramonium populations presented different variation characteristics follow different heavy metal contamination background and artificial simulation of heavy metal individual and combined pollution.For the trait of root length,the MP1 and MP2 populations experienced lead-cadmium combined pollution still maintaining growth well under lead-cadmium combined pollution of artificial simulation,and the seeding stage began to show strong growth vigor.In the control treatment(CK),the root length of MP1 and MP2 populations showed a certain ecological cost.Correspondingly,the root length of NMP1 and NMP2 populations that did not experience heavy metal pollution were inhibited by lead-cadmium combined and individual pollution treatment,respectively.At the end of the life history,the root length of populations showed a "flattening effect" in the four treatments.For the trait of plant height,Datura stramonium populations of four different material sources under heavy metal treatment,the plant height showed different degrees of decline,indicating that heavy metal pollution made plant plants dwarf.For the trait of biomass,the root and stem biomass of MP2 population maintained relatively good growth,the root and stem biomass of NMP1 and NMP2 populations were inhibited in the condition of lead and cadmium pollution.Leaf biomass showed different patterns in every growth stages with different material sources and heavy metal treatment methods,and the lead-cadmium combined pollution inhibited the leaf growth of the plants.The order of flowering time of the four populations was:NMP2,NMP1,MP2,MP1.From the delay percentage of life history,lead-cadmium combined pollution>individual pollution of cadmium>individual pollution of lead.Seed quality of population MP was higher than NMP.It was benefit for plant to increase their colonization in extreme environments(2)The resource allocation of Datura stramonium showed different responses under heavy metal pollution.Divided by different material sources,population MP1 and MP2,which have been grown for a long time in high concentration of heavy metal pollution,their life history were delayed under the treatment of artificial heavy metals.Most of the energy in the life history was used for vegetative growth,and the offspring seeds remained at a higher quality than the control population NMP1 and NMP2 population which did not experience heavy metal pollution reduced the root,stem and leaf input,increased the reproductive input under the individual and combined pollution of heavy metal of lead and cadmium.The flowering period was relatively advanced and the seed quality decreased.According to the same material source grew in CK,Pb,Cd and Pb-Cd treatments,(3)Using ISSR molecular marker technique to analyze the genetic diversity and genetic structure of Datura stramonium with different pollution experiences,the results were showed as follows:Five primers were screened from 30 ISSR primers,and 65 bands were amplified,with an average of 13 loci per primer.The polymorphic loci rates of the four populations ranged from 84.62%to 92.31%.Among them,the NMP1 population had the highest percentage of polymorphic loci,which was 92.31%,and the MP1 population had the lowest percentage of polymorphic loci,which was 84.62%.The Nei’s sene diversity and Shannon’s Information index had a good consistency on the estimation of the genetic variation of the Datura stramonium.The order of genetic diversity was:NMP1>NMP2>MP2>MP1.Using Nei to calculate the genetic differentiation of the population,the genetic diversity within the population was 0.2535.the genetic diversity between the populations was 0.0084,and the coefficient of genetic differentiation was 0.0319.The overall genetic differentiation of the four populations was small,and genetic variation remained within the population.From the genetic distance and genetic identity,a certain degree of genetic variation occurred among the four populations of Datura stramonium.The genetic distance between MP1 and MP2 populations experienced heavy metal pollution was 0.0146,the genetic distance of MP2 populations experienced heavy metal pollution and NMP2 populations without heavy metal pollution was relatively large,being 0.0219.These data suggested that the negative effects of heavy metal pollution on Datura stramonium with pollution experience tend to decline compared with non-polluting populations.Specifically,it included:the decrease in the amount of biomass decline,resources allocation for reproduction and reproduction has been changed,and tended to put more resources for vegetative growth.The genetic diversity of populations was declined.These results indicated that the pollution experience had an impact on the resistance for plant to adapt stressful environment,usually in a direction that benefited for environmental stress to differentiation. |
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