Effects Of Drought,Salinity And Nutritions Deficiency On Growth And Antioxidation Of Native And Invasive Chinese Tallow Tree

When alien plants introduce into new habitats,they can evolve many morphological and physiological characteristics which are different with the native species,even under the low resource environments.These new characteristics are beneficial to alien plants invasion.However,it is still unclear how these characteristics evolved and their roles in the adaptation of during invasion.In this paper,8 pairs populations of Triadica sebifera from China(native)and the United States(invasive)were selected during common garden experiments.Drought stress(55%-60% of field capacity)or salt stress(5 g/L Na Cl)was simulated.Deficient nutrients(no added nutrition)and different phosphorus levels(high phosphorus HP,P = 2 mmol/L,low phosphorus LP,P=0.2 mmol/L)were supplied,respectively.The activity or contents of antioxidant enzymes and non-enzymatic substances,changes of growth parameters and chlorophyll fluorescence parameter,as well as the infection rate of arbuscular mycorrhizal fungi(AMF)were determined in seedlings of native and invasive Triadica sebifera populations.The aims were to clarify the growth adaptability and physiological resistance of native and invasive populations to different environments and to discuss the roles of AMF on salt stress and different nutrition levels.The results showed:Drought,salt stress and nutrient deficiency significantly inhibited the growth of the invasive population,the invasive population still had significantly larger biomass,plant height(increase of plant height)and stem diameter(increase stem diameter).Therefore,invasive populations were more sensitive to drought stress,salt stress and nutrient deficiency compared with native ones,but it has stronger tolerance,this is mainly reflected in:1.Under drought stress,total antioxidant capacity(T-AOC),superoxide anion scavenging rate,peroxidase activity(POD)as well as vitamin E(VE)and ascorbic acid(As A)contents were significantly higher(the populations of the invasive site was 1.19-3.05 times that of the native populations),but MDA(malondialdehyde)and H2O2(hydrogen peroxide)contents were lower in invasive populations than those in native ones.Simutaneously,they had similar superoxide dismutase(SOD)activity and hydroxyl radical scavenging rate,as well as higher synthetically membership function values.2.Compared with the native populations,the invasive populations had significantly less reactive oxygen species accumulation(the populations of the invasive site was 69%-92% that of the native populations),relatively higher T-AOC as well as larger free radical scavenging rate(the populations of the invasive site was 1.01-1.19 times that of the native populations)under salt stress.At the same time,salt stress promoted higher AMF infection rate in invasive populations compared with non-salt stressed seedlings of native populations.Under adequate nutrition,salt stress significantly reduced the ETR(I),Y(I),ETR(II),Y(II),Fv/Fm and q P of native populations,but raised those of the invasive populations.Nutrient deficit did not aggravated ETR etal of salt-stressed native and invasive populations,there were also no significant differences between origins.However,nutrient deficit weakened AMF roles in growth promotion.3.The growth and physiological performance in native and invasive Triadica sebifera seedlings were different at different phosphorus levels.Compared with the native populations,under low phosphorus(LP),ETR were the smaller and Fv/Fm,q P was the larger in invasive populations,invasive populations have stronger photosynthesis ability under high phosphorus(HP).Compared with the native populations,under low phosphorus,invasive population accumulated less superoxide anion and H2O2(the populations of the invasive site was 69%-91% that of the native populations),but improved higher SOD activity,hydroxy radical and superoxide anion free scavenging rate and T-AOC(the populations of the invasive site was 1.01-1.19 times that of the native populations).Importantly,the AMF infection rate of the invasive populations was significantly higher than that of native populations.Therefore,the invasive population has better tolerance to HP and LP environment,and the native population is intolerant the HP environment.In conclusion,compared with the native populations,the invasive populations were more sensitive to drought stress,salinity,nutrient deficit or their coupling treatments with more growth decrease and changes of photosynthesis.However,the invasive populations had stronger antioxidant capacity and light energy protection mechanism so as to maintaining larger growth advantage,i.e.invasive populations had stronger physiological resistance compared with native populations.AMF played positive regulation role under conditions of deficient nutrition(non-salt stress).