Population Ecological Differentiation Of Vicia Faba L. And Zea May L. Under Persistent Pollution Of Pb, Cd

The population ecological differentiation about the plant growing under the persisting polluted environment is an important issue in pollution ecology. The study chose three varieties of broadbean (Vicia faba L)(marked respectively as A, B and C in the context) and three varieties of maize (Zea may L)(marked respectively as Z1, Z2and Z3in the context) cultivated in the field polluted by Pb (40mg/kg,250mg/kg), Cd (10mg/kg,60mg/kg) and combined treatment of Cd and Pb (Cd20mg/kg+Pb60mg/kg). Through the analysis of quantitative characteristics, eco-physiological characteristics and molecular markers to discussed the change of population structure and Population Ecological Differentiation. The results were showed as follows:(1) The quantitative characteristics of broadbean and maize were changed with different species and concentrations of pollution. Some change of indicators had significant differences, but some showed consistency. For the trait of vegetative growth, the heavy metal pollution leaded to the brachysm of broadbean and maize population, at the same time the stem dimension of maize and the first legume height of broadbean were decreased. Three varieties of broadbean showed ecological differentiation on adaptive strategy about the trait of reproductive respect, such as variety A and B decreased the gross of seed and improved the quality of seed to guarantee the competitiveness of descendant, but variety C increased the number of seed and decreased the weight of seed. For the maize, heavy metal pollution depressed their vegetative growth, Z3variety was particularly evident, this result matched with the consequence of perturbation test about resistance of different populations.(2) The physiological responses of the broadbean and maize populations treated with heavy metal pollution were different. As to the enzyme system, heavy metal pollution made POD enzyme activity and MDA content significantly changed. Such as the POD enzyme activity of variety A and C of broadbean were increased at40mg/kg Pb polluted, and decreased at250mg/kg Pb polluted, the POD enzyme activity of variety B was decreased at all polluted conditions. The POD enzyme activity of variety Z2and Z3of maize were increased at40mg/kg Pb and60mg/kg Cd polluted, decreased at other polluted conditions. The MDA content of all the varieties of broadbean and maize were decreased at lower heavy metal pollution and increased at higher heavy metal pollution.In the aspect of resources access, vast majority populations of broadbean and maize improved their content of chlorophyll to make sure the synthesize of organic substance, but the chlorophyll fluorescence information showed that the Fv/Fm of broadbena and maize was decreased under heavy metal pollution. It means that heavy metal destroyed the chloroplast microstructure and damaged photosystem. In terms of nutrient element allocation, different varieties of broadbean and maize chose different adaptation strategies under heavy metal pollution. Such as variety A of broadbean enhanced its reproductive ability but variety B enhanced its vegetative growth in order to preempt the resources to adapt the pollution environment. Under heavy metal pollution different organs of maize had different variation tendency of N and P content, but all populations increased their N content in the stem and leaf to make sure their vegetative growth.In the aspect of energy allocation, three varieties of broadbean chose to reduce the energy input of vegetative organs and increase the energy input of reproductive organs to ensure the quality of later generations. The energy input of defense system of broadbean also increased at initial stage, but later declined with the increase of reproductive energy input. The energy input of maize populations decreased in stem and leaf but increased in root with the rise of heavy metal concentration, this was beneficial for absorption and fixation of root in stress environment. (3) The ISSR molecular marker shower that the heavy metal pollution influenced the genetic diversity in broadbean and maize population had two aspects:reduced or increased the genetic diversity, which was related to the variety of population, to the heavy metal concentration. The heavy metal leaded to population’s genetic diversity changed, and this changed was related to the population’s sensitive degree for pollutants, to the mutag of pollutants, to the initial population size and to the genetic reserves of initial population. Through the calculation of the population genetic distance found that heavy metals had huge impact on genetic differentiation of broadbean and maize, and this impact was associated with plant species and polluted time. The results also showed that the higher of population’s resistance level the smaller of genetic structure influenced by heavy metal pollution and the smaller of the genetic differentiation of population.(4) According to the Perturbation test, a curtain variety could have different adaptation to different pollution and the adaptation among different varieties was not identical. The order of adaptation in three varieties of broadbean was:B>A>C, the order of adaptation in three varieties of maize was:Z2>Z1>Z3.Correlation analysis showed that the genetic diversity indices had opposed correlativity with the population response (PTB value). The related coefficient of Ne, H and I had reached the extremely significant level and could reflect the population genetic structure more reliable.