Response Of Physiologic Indexes And Electrical Impedance Of White Birch To Waterlogging And Flooding Stresses

White birch (Betula platyphylla Suk.) is an important native tree in northern Chinaand the excellent tree of afforestation in the region and mountainous areas. In thisexperiment,2-year-old white birch seedlings under waterlogging and flooding stresses (CK:normal; treatment A: waterlogging stress; treatment B: flooding stress) were studied bymean of a series of physiologic indexes (endogenous hormones, soluble sugar, starch,nutrient element and so on) to discuss mechanism of waterlogging resistance of white birch.Meanwhile, the electrical impedance spectroscopy (EIS) parameters of roots of white birchseedling were measured, and the change rules of the parameters after waterlogging andflooding stresses treatments were obtained. The correlations of the EIS parameters withtested physiologic indexes were analyzed to find the best parameters which can expressphysiological status of the white birch roots under waterlogging and flooding stresses, andprovide a technical method for fast monitoring and assessing physiological status andgrowth of plant roots under adverse situation. In addition, the EIS, water content andmembrane permeability of leaves and stems of white birch seedling under flooding stresswere measured, and the correlations of the EIS parameters with water content andmembrane permeability were analyzed to find the best parameters which can buildestimating models with water content change and assess threshold value offlooding-enduring time in white birch under flooding stress. The aim was to promotepractical application of EIS technology and offer important theoretical foundation andtechnical support by applying EIS technology to estimate water content change andthreshold value of flooding-enduring time. Main results are as follows:1. Following the prolong of stress treatments time, chlorophyll content, netphotosynthetic rate (Pn), transpiration rate (E), stomatal conductance (gs), the chlorophyllfluorescence parameters quantum yield of photosystem Ⅱ electron transport (ΦPSⅡ),apparent photosynthetic electron transport rate (ETR), maximal photochemical efficiencyof photosystemⅡ(Fv/Fm), and the photochemical quenching coefficient (qP) decreased,whereas the intercellular CO2concentration (Ci) and non-photochemical quenchingcoefficient (qN) increased. It indicated that photosynthesis of white birch leaves get seriousinhibition under waterlogging and flooding stresses.2. Following the prolong of stress treatments time, in leaves under waterloggingtreatment, ABA, IAA, ZR, IAA/ABA, ZR/ABA and (GA+IAA+ZR)/ABA increased.GA and GA/ABA firstly increased, and then decreased. In stems under waterloggingtreatment, ABA firstly increased, then decreased, finally increased again. ZR, GA, IAA/ABA and GA/ABA decreased. IAA, ZR/ABA and (GA+IAA+ZR)/ABA firstlydecreased, then increased, finally decreased again. In roots under waterlogging treatment,ABA, GA and GA/ABA firstly decreased, then increased, finally decreased again. IAAfirstly increased, and then decreased. ZR and ZR/ABA firstly decreased, and thenincreased. IAA/ABA and (GA+IAA+ZR)/ABA decreased. In leaves under floodingtreatment, ABA, GA, ZR, ZR/ABA, and GA/ABA firstly decreased, and then increased.IAA, IAA/ABA and (GA+IAA+ZR)/ABA increased. Change of content and ratio ofeach endogenous hormone in stems under waterlogging and flooding treatments were thesame. Change of content and ratio of others endogenous hormone in roots underwaterlogging and flooding treatments were the same except ABA and IAA/ABA. ABAfirstly increased, and then decreased. Change trend of IAA/ABA and ABA were reverse.3. Following the prolong of stress treatments time, under waterlogging treatment, Nfirstly increased, and then decreased in roots, stems and leaves. P decreased in stems andleaves, while P firstly increased, and then decreased in roots. Mn increased in roots, andfirstly decreased, then increased, and finally decreased again in stems and leaves. Fedecreased in roots and stems, whereas firstly increased, and then decreased in leaves. K, Ca,Mg, Zn and Cu decreased in roots, stems and leaves. Under flooding treatment, N, K, Mg,Ca, Zn, Fe and Cu decreased, whereas Mn increased in roots, stems and leaves. Pdecreased in stems and leaves, while firstly increased, and then decreased in roots.4. Following the prolong of stress treatments time, under waterlogging treatment, thesoluble sugar content increased in leaves and stems, whereas firstly decreased, and thenincreased in roots. The starch content increased in leaves and roots, whereas firstlyincreased, and then decreased in stems. Under flooding treatment, the soluble sugar contentfirstly increased, and then decreased in roots, stems and leaves. The starch content firstlyincreased, and then decreased in leaves and stems, whereas firstly decreased, and thenincreased in roots.5. Roots of white birch seedlings generated adventitious roots by waterlogging andflooding treatments, and waterlogging treatment generated adventitious roots more thanflooding treatment; the dry matter contents were significantly lower than normal treatmentin roots under waterlogging and flooding treatments on the60th day. The EIS parameterschanged during stress treatments, and the change of specific extracellular resistance (re)was the same as relaxation time ().6. During waterlogging and flooding treatments, rewas mainly impacted by thesoluble sugar, IAA, and Ca. The reexisted a significant positive relation with the solublesugar and IAA respectively, whereas reand Ca had a significant negative correlation inroots. The was mainly impacted by N and a significant negative correlation was found inroots. The distribution coefficient of relaxation time () was mainly impacted by the starch,K, Cu, Zn, and GA/ABA. The and the starch existed a significant negative correlation, whereas the had a significant positive relation with K, Cu, Zn, and GA/ABA respectivelyin roots.7. With the increasing in treatment duration of flooding stress, water contents ofleaves and stems decreased under flooding treatment. The reactance value in EIS top arc ofleaves decreased under flooding stress, and for stems it increased firstly, and thendecreased. Under flooding stress, the water contents and membrane permeability withsome parameters of the EIS in leaves and stems correlated significantly. The EISparameters correlated with the water content of leaves and stems under flooding stresswere selected to establish estimation models. Among them the specific high-frequencyresistance r estimated best for the water content of leaves and stems. The best estimationmodels were yleaf=1.0668e-0.11xand ystem=0.0007x2+0.0037x+0.5254, respectively.