Effects Of Clonal Integration On Spread Of Paspalum Paspaloides And Leersia Japonica From Terrestrial To Aquatic Habitats

The interconnected individuals(ramets)of the same clonal plant have the ability to translocate water,nutrients and carbohydrates via stolons or rhizomes,i.e.clonal integration.Clonal integration can effectively improve growth and facilitate spread of clonal plants in heterogeneous environments,and also increase resistance of ramets under unfavorable conditions.Water nutrient,salinity and heavy metal contamination are common environmental pollution in natural wetlands.However,whether clonal integration can improve the capability of wetland clonal plants to spread from terrestrial to polluted aquatic habitats remains to be further studied.Two common wetland species Paspalum paspaloides and Leersia japonica were selected for the study.By conducting greenhouse simulation experiment,we aimed to investigate the effect of clonal integration on growth and physiological characteristics of the apical ramets and the basal ramets as well as the whole fragments of these species,in the condition of spreading from terrestrial to aquatic habitats with the different nutrient levels of P.paspaloides and L.japonica,and the different salinity and cadmium pollution levels of P.paspaloides.The results showed that the disconnected treatment(without clonal integration)significantly increased the growth and photosynthetic capacities of the apical ramets of P.paspaloides and L.japonica distributed in the high-nutrient water,but had no significant effect on the growth of the whole fragments.However,nutrient application pattern had no significant effect on the growth of either the ramet level or the whole fragment level.The higher the initial node ratio between apical and basal ramets was,the higher the total biomass of the whole fragments would be.Compared with plants without clonal integration,plants with the integration significantly increased the leaf growth and photosynthetic capacities of the apical ramets of P.paspaloides distributed in the salinity water,such effect increased with the increase of salinity concentration.However,clonal integration did not significantly affect the growth of the whole fragments.The leaf mass ratio of the connected to the disconnected treatment was higher at the level of 250 mmol L-1.The total mass ratio of the connected to the disconnected treatment was higher at the level of 150 mmol L-1.Clonal integration also increased the growth of the apical ramets in the cadmium-contaminated water,such effect increased with the increase of cadmium concentration.Meanwhile,at the cadmium contamination levels of 4 mg L-1 and 12 mg L-1,clonal integration significantly improved the growth of the basal ramets and the whole fragments.With clonal integration,Na+and Cd2+could be translocated from the apical ramets in the salinity and cadmium contaminated water to the non-contaminated basal ramets;therefore,it can effectively alleviate impacts of toxic ions on the growth apical ramets.Clonal integration had no significant effect on the growth of these species when spreading from low-nutrient terrestrial habitats to high-nutrient aquatic habitats.However,the integration could greatly improve the growth and the spread of the apical ramets from uncontaminated terrestrial habitats to contaminated aquatic habitats,as well as the growth of the basal ramets and the whole fragments under certain cadmium contamination levels.Clarifying the role of clonal integration in the expansion of wetland clonal plants at riparian region would improve the basic theoretical research on clonal plant ecology and provide a theoretical basis for vegetation restoration and reconstruction of polluted wetlands.