Effects Of Salt Conditions On The Roots Of Tamarix Chinensis In The Yellow River Delta Wetland

Root as a key functional organ in plant has a key role in growing process.who has an important role in anchorage and water and nutrient acquirement,as well as synthesis and storage of metabolites.The normal development of root as an important base of plants healthy development has important significance in the process of life.In the growing process of plants,root with water,soil,air and microbial connect interface,which is the key link between the plant community and the surrounding environment to realize the material cycle and energy flow,it plays an important role in the ecological functions of plants and the maintenance of ecological balance.The Yellow River delta wetland as the youngest and most characteristic wetland in China is located on the sea-land interface,which has a unique ecological environment and frequent natural disasters.Therefore it shows the characteristics of complexity,instability and vulnerability.High soil salinity in the Yellow River Delta due to some factors such as tidal erosion,river break and precipitation decrease,which leads to a higher requirement for plant growth and survival.Tamarix chinensis is a dominant shrub in the Yellow River Delta region,which can effectively exclude salt from the plant.However,the roots can directly sense soil salinity changes,which mean that the effect of differing salinity on the eco-physiological characteristics of roots of Tamarix chinensis cuttings is very important for the ecological restoration of coastal wetlands.In the present study,we studied by control experiment in greenhouse,the means of field investigation and laboratory analysis on the eco-physiological characteristics of roots of 1-year old Tamarix chinensis.To explore the response of Tamarix chinensis root growth and eco-physiological characteristics to different salinity levels.It provides a scientific basis for the ecological protection and restoration of coastal wetlands,as well as the restoration of plants in saline environment,which is of great significance to the development and sustainable utilization of wetland resources in the Yellow River Delta.Based on the field investigation,field experiment,solution culture experiment in greenhouse and data collection in the past two years of 2015-2017,a large number of detailed and reliable data were obtained.Main results obtained as follow:(1)under different environmental conditions,Tamarix chinensis has different root depth,with soil moisture content,the distance from the sea,and salinity and soil water soluble salt content has a close relationship.The principal component analysis found further,soil water soluble salt content is the main environmental factors that affects the Tamarix chinensis root shoot ratio,soil water soluble salt content is higher,the greater the root shoot ratio of Tamarix chinensis.Different environment conditions of typical allometric growth relationship between root cap,for long-term way of self-regulation to adapt to the environment conditions.Ion content is arranged according to difference in degree,and its order was: Na+ > Ca2+ > Mg2+> K+.The distribution of Na+ content of Tamarix chinensis was the dominant position,which is mainly distributed in the stem and leaf parts,less in the root distribution.The distribution of Ca2+ and Mg2+ of Tamarix chinensis are similar,which are mainly distributed in leaves and roots.Correlational analyses shows,there is significant correlation between K+,Na+,Ca2+ and Mg2+ of Tamarix chinensis.(2)We studied the effects of different salinityon the eco-physiological characteristics of roots of 1-year old Tamarix chainensis and Tamarix austromongolica,the results showed that: in the treatment of 0.8% NaCl,the rooting rate of T.chainensis was about 83%,the rooting rate of Tamarix austromongolica was about 36%;the Tamarix austromongolica was without rooting in the treatment of 3.6% NaCl.The rooting rate and the life of root of two species of Tamarix decreased significantly when the salinity increased to more than 0.8%.The root growth of two species of Tamarix were significantly inhibited when the salinity increased to more than 1.2%.The biomass allocation pattern of Tamarix chainensis and Tamarix austromongolica adjustment to acclimate to salinity conditions,proportion of root biomass increased gradually.However,The root biomass of Tamarix chainensis was still less than the aboveground biomass;the root biomass of Tamarix austromongolica gradually increased with increasing salinity,the percentage of root biomass was higher than that of aboveground biomass once the salinity was greater than 1.2%.(3)The activity of ATP synthase and the activity of CAT of Tamarix chainensis increased when the salinity were less than 0.8%,and the activity decreased when the salt content was more than 0.8%.The content of abscisic acid(ABA)of Tamarix chainensis root increased with the increasing salinity,and then decreased when the salinity increased to more than 1.2%.The activity of ATP synthase and the activity of CAT and the content of ABA of Tamarix austromongolica gradually decreased with increasing the salinity.(4)The effects of salt conditions on the root system of Tamarix chinensis that was studied in field investigation experiment and indoor hydroponics experimen was mainly in the following aspects: in the natural habitat and hydroponics experiments,the biomass allocation model of Tamarix chinensis showed similarity under high salt conditions,the proportion of biomass will lean toward the root,the allocation model can increase root uptake of water and nutrients,it is beneficial to dilute the intracellular salt and enhance the ability of plants to adapt to the salted environment.Root cap of Tamarix chinensis shows a constant growth rate in natural habitats,which is a long-term adaptation to the ecological environment of the Yellow River Delta salinization under the natural conditions.Comparison of growth and physiological characteristics of Tamarix chinensis and Tamarix austromongolica under the condition of water cultivation,after excluding the environmental conditions of soil,the root data obtained can objectively reflect the essential differences of the genetic characteristics of roots.Tamarix chinensis and Tamarix austromongolica under salinity conditions showed some adaptability.Comprehensive analysis the rooting and root growth of Tamarix chinensis and Tamarix austromongolica under different salinity conditions,the relatively good performance of Tamarix chinensis,which provides valuable information for the selection of tree species for revegetation of coastal wetlands in the Yellow River Delta.