The Strategies Of Resource Allocation In The 18th Generation Vicia Faba L. And Zea Mays L. Continously Exposed To Pb And Cd Pollution

In the past,research focuses mainly on the response of organisms to acute high-dose pollutants.The impact of long-term,persistent pollution on the adaptation and evolution of plants has not been systematically studied.However,an understanding of the effects of persistent pollutants on plant phenotypic traits and resource allocation strategies is critical for determining whether plants can adapt to heavy metal pollution,as well as how pollution stress influences ecological strategies.In this study,we tested two treatment levels of simulated soil heavy metal concentrations of cadmium(Cd 10 mg/kg and Cd 60 mg/kg)and lead(Pb 40 mg/kg and Pb 250 mg/kg),and one treatment level of the two metals combined(Cd 20 mg/kg + Pb 60 mg/kg);our study species was Vicia faba L.and Zea mays L.;we used three V.faba and Zea mays L.varieties that had been planted on contaminated soil for 17 generations.This paper analyzes from the three aspects of quantitative traits,photosynthetic capacity and resource allocation,and initially explores the characteristics of resource allocation strategies of plants in the process of adapting to heavy metal pollution under long-term continuous pollution.The research results are as follows:(1)Quantitative traits of Vicia faba L.and Zea mays L.populations under continuous heavy metal pollution conditions showed different changes due to different plant species,growth periods,heavy metal species,and pollution concentrations.Pb and Cd pollution generally causes dwarfing of broad bean and corn plants at the seedling stage,The plant height and stem thickness of the broad bean and corn populations have different growth rates at different growth and development stages,Overall,plant height and stem thickness in plants exposed to heavy metal pollution exhibited different growth rates at across growth stages;At the same time,the root and ear position ratios of broad bean and corn populations showed low concentration pollution to promote growth,and high concentration pollution to inhibit growth.From the perspective of reproductive indicators,The high concentration of Cd pollution significantly greater numbers of flowers,pods,and seeds per pod.Notably,seed weight was significantly reduced,suggesting a shift towards an r-selection reproductive strategy.Under the condition of compound pollution,some broad bean populations can reduce the number of seeds while improving the quality of seeds,suggesting a shift towards an K-selection reproductive strategy.The number of female flowers and the length of tassel in the corn population showed a change pattern that first increased and then decreased with the increase of pollution concentration.Broad bean and corn can be propagated after 18 generations of Pb and Cd continuous pollution conditions,but the reproduction strategy has been differentiated.(2)The persistent pollution of Pb and Cd had significant effects on the light and capacity of broad bean and corn populations,reflects the restrictions on the ability to obtain carbon resources.Pb and Cd pollution reduced the chlorophyll content of broad bean and corn populations,although there are differences between the varieties of broad bean stomatal conductance and transpiration rate,but the photosynthetic rate of broad bean populations decreased significantly under Pb and Cd pollution.At the same time,the photosynthetic rate,stomatal conductance and transpiration rate of Zea mays L.populations decreased significantly under Pb and Cd pollution.(3)Under the condition of continuous pollution of Pb and Cd,the two plants as a whole tend to reduce the allocation of underground biomass,and the proportion of aboveground biomass increases and the tendency to increase reproductive input is obvious.Continuous pollution of Pb and Cd affects the biomass and configuration of broad beans and corn.The Zea mays L.population increased reproductive input,and reduced the distribution of underground biomass and stem and leaf input.The law of biomass allocation of broad bean populations is more complicated: Under Pb pollution conditions,broad bean plants reduced the distribution of underground biomass,and increased the input of stems and leaves to ensure vegetative growth.Under the condition of Cd pollution,as the concentration of pollutants increased,the broad bean population reduced the input of stem and leaf and underground biomass,and increased the reproductive input.(4)Under the conditions of this study,the total calorific value of broad bean and corn populations in a single pollution increased at a small dose,and with the increase of the concentration of pollutants,there was a significant downward trend at a large dose,The total energy of broad bean and corn populations decreased significantly under the condition of compound pollution.Under the continuous pollution conditions of Pb and Cd,the two plants as a whole tend to reduce the energy distribution of the underground part,and the proportion of the above-ground part energy increases,and the tendency to increase the reproductive energy input is obvious.But some broad bean populations are different under Pb pollution.