| Extoxic plant invasion has caused severe harm to global and regional biodiversity,environment and economy.Most of successful exotic invasive plants are clonal plants with strong clonal reproductive ability,and the effect of clonal properties on plant invasiveness has not been researched thoroughly.Alternanthera philoxeroides is a notorious invasive plant,however,little is known about the effects of clonal traits(clonal integration)on invasiveness,especially for the influence of different ecotype plants.So we choosed two ecotypes of A.philoxeroideos(terrestrial and aquatic plants)as major research object in this study.We designed greenhouse controlled experiment to simulate three typical heterogeneous habitats that plants may meet in the process of invasion.Hope to investigate the contribution and mechanism of clonal integration on A.philoxeroides invading to different habitats,and clarify the role of clonal integration in A.philoxeroides successful invasion,thus provide new theoretical foundation to the prevention and control of A.philoxeroides.The main results as follows:(1)To simulate the heterogeneous interference habitats of plant growing in natural conditions,we sheared the apical ramets of two ecotypes of A.philoxeroides(terrestrial and aquatic)with four levels(no defoliation,20%,50%,90% of leaf area),and kept stoloniferous connected or severed to test the effects of clonal integration.Our results showed that defoliation greatly decreased the performance(biomass,ramet number)of apical ramets,clonal integration significantly improved the growth and physiology performance,and these effects were larger under heavier defoliation.Moreover,clonal integration markedly facilited the root/shoot ratio of A.philoxeroides to uptake resources effectively in defoliation,and the increase of soluble suger and total phenolic may help the invasive plant compensate for the leaf clipping and mitigate the negative impacts.These effects of clonal integration were more important on aquatic A.philoxeroides.(2)To minic the heterogeneous light environment in natural habitats,we set the shading condition of 80% full sunlight intensity or no shading of the apical ramets on two ecotypes of A.philoxeroides(terrestrial and aquatic),and planted experimenter in soil and water condition respectively,furthermore,kept stoloniferous connected or severed to exaim the effects of clonal integration,and then compared the effect of shading and substrate.Our finding suggested that shading greatly decreased the performance of A.philoxeroides in both substrate,and these effects were more notable in aquatic condition.Clonal integration greatly enhanced the performance of apical ramets,and help to improve the growth of clonal-system.Moreover,terrestrial plant showed a distinct maternal effect and show a clear advantage in soil condition in comparison with aquatic plants.(3)To simulate the heterogeneous metal polluted conditions in natural environment,three levels of metal concentration were added in apical or basal ramets respectively,kept stoloniferous connected or severed to test the effects of clonal integration.We aimed to explore the role of clonal integration on growth of stoloniferous herb A.philoxeroides suffering from heterogeneous pollution habitats.Our finding showed that the metal icon absorbed by root,transported to other organs,and accumulated in each parts of plant,and produces poisonous effects.The apical metal pollution remarkable decreased the biomass,ramet number,leaf number and stem length,connected basal parts also supressed in heavy(50ppm)pollution.The basal metal pollution affected both the performance of apical and basal ramets.Clonal integration alleviate the negative effects on growth of apical ramets suffering from heavy metal stress,and decreased the root/shoot ratio of polluted ramets,reduced the icon accumulation.These effects may benefical for the growth of A.philoxeroides suffering the heterogeneous heavy metal polluted habitats. |
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