Impacts Of Endocrine Disrupting Chemicals Bisphenol A On The Life-history Strategies Of Vallisneria Natans And Vallisneria Spinulosa

The endocrine disrupting chemicals Bisphenol A（BPA）is a new contaminant that can interfere with the normal life activities of living organisms.It has become a global environmental problem through leakage of wastewater and waste liquids into water ecosystems.Most studies on BPA have focused on animals and terrestrial plants.For aquatic plants,studies have shown that high concentrations of BPA cause significant toxicity to aquatic plants,while the effects of BPA at concentrations below environmental levels on aquatic plants are unclear.Submerged plants are important primary producers in freshwater lakes,providing food and habitat for aquatic organisms while maintaining clear water stability,therefore,studying the effects of low concentrations of BPA on the life history of submerged macrophyte is of great importance to freshwater ecosystems.Vallisneria L.are pioneering plants for freshwater ecosystem restoration and are also considered to be excellent materials for mitigating the level of eutrophication in water bodies and re-establishing aquatic vegetation.In this study,the dioecious annual submerged macrophyte Vallisneria natans（Lour.）Ha-ra and Vallisneria spinulosa Yan were used as experimental materials to investigate the life-history responses to different concentrations of BPA(targeting at 0.01,0.1 and 1 mg·L^-1)exposure,providing a theoretical basis for revealing the ecotoxic mechanism of BPA on aquatic plants and a reference for assessing the potential ecological risk of BPA exposure in aquatic ecosystems.The main results are as follows.（1）Impacts of BPA on the life-history strategies of Vallisneria natansAt the seedling growth phase,the highest concentration of BPA(1 mg·L^-1)inhibited the elongation of V.natans leaves and promoted an increase in the number of leaves and the number of ramets.For mature individuals of V.natans,1 mg·L^-1 BPA treatment also significantly reduced the maximum leaf length and increased the number of leaves,the number of ramets and leaf area;physiological indicators（total carbon,soluble sugar content and soluble sugar content）of V.natans leaves were significantly affected by BPA,with total carbon and soluble sugar content significantly increased and total nitrogen content significantly decreased under under 1 mg·L^-1 BPA treatment.The biomass of mature individuals remained stable after BPA treatment.At the highest concentration of BPA(1 mg·L^-1),the number of ramets of female individuals of V.natans was significantly lower than that of males.The number of female flowers as well as the number of fruits of V.natans were not statistically between treatments,however,the germination of seeds produced after treatment with the highest concentration of Bisphenol A(1 mg·L^-1)was significantly inhibited.These results indicated that the leaf growth of V.natans were affected by BPA treatment,and the reproductive characteristics of mature individuals were not significantly affected,but the germination of seeds was severely inhibited.BPA did not cause direct toxicity during the growth phase of V.natans,which tolerated the effects of BPA through trade-offs between leaves.Although V.natans treated with BPA can maintain stable flower and fruit production,the germination rate of the seeds it produced was significantly reduced,and its serious consequences should be further studied.（2）Impacts of BPA on the life-history strategies of Vallisneria spinulosaThe leaf growth of V.spinulosa was significantly inhibited,the lowest concentration of bisphenol A(0.01 mg·L^-1)inhibiting the elongation of V.spinulosa leaves,while higher concentrations of bisphenol A(0.1 mg·L^-1 and 1 mg·L^-1)reducing the number of leaves,the number of ramets and seedling survival rate.For mature individuals,there was no significant differences in growth traits（leaf morphology and biomass）of V.spinulosa leaves between the different BPA concentrations.The soluble sugars and total carbon content of mature leaves decreased and total nitrogen content increased under different BPA concentrations.For reproductive traits,the highest concentration of BPA(1 mg·L^-1)BPA significantly reduced the biomass of winter buds of asexual reproduction of V.spinulosa,and there was no statistically significant difference in total carbon and total nitrogen contents of winter buds among the experimental treatments.Thus,BPA treatment inhibited the growth of V.spinulosa seedlings,and the growth traits of mature individuals remain stable,but the reproductive traits of mature individuals were significantly inhibited by BPA.In summary,exposure to BPA has an impact on the life-history strategies of V.natans and V.spinulosa,with significant effects on the growth stage of seedlings.V.natans and V.spinulosa ensuring stable individual biomass through leaf phenotypic plasticity and the trade-off between traits.BPA caused significant stress on reproduction in both V.natans and V.spinulosa,and a higher concentration of BPA inhibited the germination of seeds of V.natans and the biomass of winter buds of asexual reproductive organ of V.spinulosa.As the main food for some rare waterfowl during the winter season,As the main food for some rare waterfowl during the winter season,is a cause for concern.