Ecological Adaptation Of Phragmites Australis To Water-salt Heterogeneity In Coastal Wetland Of The Yellow River Delta

The soil salinization in the Yellow River Delta has seriously restricted local ecological stability and development.Phragmites australis,a typical wetland plant,is usually selected to be the preferred species for wetland restoration and reconstruction,because of its powerful phenotypic plasticity and clonal integration ability and tolerance to different degrees of water and salt stress.In this study,we chose the P.australis to be the objective material to explore:(1)the different growth in two saline habitats.(2)the characteristics of physiological and ecological adaptation under the combination of salinity and clonal integration.The main conclusions were as follows:(1)In the two saline habitats,the soil electrical conductivity decreased first and then increased with the deepening of soil depth.The salt stress to P.australis was more serious in tidal habitat.The average density,plant height and total biomass of P.australis in tidal habitat were lower than those in freshwater habitat.(2)The proportion of biomass of P.australis distributed in the main root in two water and salt habitats was more than 50%.The distribution proportion of aboveground biomass(stem and leaf)of P.australis in fresh water area is higher than that in tidal area,and the distribution proportion of underground biomass(main root and fibrous root)in tidal water area is larger.The content of Na⁺in the main root of P.australis in tidal water was higher than that in fresh water,however the situation of K⁺was just the opposite.(3)The plant height,stomatal conductance,underground and aboveground biomass were all inhibited by 2%homogeneous salt both in clonal integration and non clonal integration treatments.The Na⁺content in all parts of the P.australis increased significantly.(4)In the 1%total salinity treatment,the high part(2%)and low part(0)treatment,the net photosynthetic rate,transpiration rate,total underground and aboveground biomass and K⁺content of main root of P.australis under clonal integration treatment were significantly higher than those without clonal integration treatment.In clonal integration treatment,the plant height and underground per plant biomass of P.australis under heterogeneous 0 salinity treatment and the CO₂concentration between cells and Na⁺content in leaves of P.australis under the heterogeneous 2%salt treatment were significantly higher than these without clonal integration.(5)In the 2%total salinity treatment,the net photosynthetic rate,CO₂concentration and transpiration rate of P.australis treated with heterogeneous 3%salt,the plant height,leaf length,leaf width,total aboveground biomass,net photosynthetic rate and Na⁺content in stem under heterogeneous 1%salt treatment under the action of clonal integration were significantly larger than that of P.australis without clonal integration.(6)2%homogeneous salt has significantly promoted the proline content in leaves of non clonal integration P.australis.In high salt part of 1%and 2%total salinity(2%and 3%Na Cl respectively),the proline content of P.australis was significantly raised by non clonal integration treatment,however this phenomenon was not found on the lower salinity side(0%and 1%salinity separately).In conclusion,P.australis in both habitats were subjected to different degrees of salt stress,the salt stress of P.australis in tidal area was higher.However,P.australis can adapt to salt stress by adjusting its morphological characteristics,biomass allocation ratio and ion balance.Clonal integration can improve the morphological and physiological characteristics of P.australis to adapt to salt stress,but it can not alleviate the ion toxicity.