| The rules of electrical impedance spectroscopy parameters, physiological parameters, relation between electrical impedance spectroscopy parameters and physiological parameters of wheat leaves are researched, which are stressed in soil drought, PEG, heavy metal ions of solution, exogenous heavy metal ions of soil, NaCl and low temperature.The effect of changes for above environmental factors on the electrical impedance spectroscopy parameters of wheat leaves is revealed. The rules of relation between electrical impedance spectroscopy parameters and physiological parameters of wheat leaves are discussed. Variable information for cell membrane of wheat leaves is reflected by electrical impedance spectroscopy parameters under environmental factors stress. Primary parameters are offered in diagnosis for the degree of wheat leaves stressed by physical index under drought, pollution of heavy metal ions, NaCl and low temperature stress.The major research results are as follows:1 The impedance spectra and equivalent circuit of wheat leaveThe impedance spectra of wheat leave segments consisted of one arc with a depression center in a complex plane between 80Hz and 1MHz. There was no clear change in the shape of the spectrum with the variation for environmental factors and stress degree except amplitude and specific frequency. Single-DCE model is the suitable equivalent circuit for wheat leave.2 The effect of soil drought on electrical impedance spectroscopy parameters of wheat leaves Between different varieties, intracellular resistance and distribution coefficient of the relaxation time show extremely significant difference but relaxation time shows significant difference. Extracellular resistance and intracellular resistance show extremely significant difference between different growing period and moisture treatment. Intracellular resistance shows significant difference in interaction of variety and moisture treatment.Electrical impedance spectroscopy parameters of wheat leaves behave alternative between different drought resisting types of wheats and aren't provided with coincidence relation with drought resistance. Extracellular resistance, intracellular resistance and distribution coefficient of the relaxation time increase and relaxation time decreases.The effects of different growing period on extracellular resistance and relaxation time is inflorescence>booting stage>heading period>filling period. The effects of different growing period on intracellular resistance is inflorescence>heading period>filling period> booting stage. The effects of different growing period on distribution coefficient of the relaxation time is inflorescence> booting stage >filling period>heading period.3 The effect of PEG stress on electrical impedance spectroscopy parameters of wheat leaves Four electrical impedance spectroscopy parameters are provided with extremely significant difference between variety, osmotic potential and time. Intracellular resistance shows extremely significant difference in interaction of variety and osmotic potential.Electrical impedance parameters are provided with extremely significant difference in interaction of variety and time except extracellular resistance, which doesn't show significant. There is significant difference between A, B, E and C, D but no significant difference among A, B, E or C, D. The discrepancy of variety on electrical impedance parameters decreases gradually with aggravating stress.The rules of electrical impedance parameters along with variation of varieties are: extracellular resistance, dryland >dry-fertilizer> irrigated area. intracellular resistance, dry-fertilizer > irrigated area>dryland, relaxation time, dryland>dry-fertilizer > irrigated area, distribution coefficient of the relaxation time , irrigated area>dryland and dry-fertilizer. The values of extracellular resistance and relaxation time are high when osmotic potential is -0.4 MPa, -0.2 MPa or low when osmotic potential is -1.0MPa, -1.2 MPa.Intracellular resistance is highest when osmotic potential is -0.8 MPa and lowest at CK. Distribution coefficient of the relaxation time is highest when osmotic potential is–1.2MPa or lowest when osmotic potential is -0.2MPa.The values of extracellular resistance and relaxation time are highest at control time and lowest at 72h, which decrease significantly with time extending. The values of intracellular resistance and distribution coefficient of the relaxation time are highest at 72h and lowest at control time.For variety A, B, C, E, there is significantly positive correlation or extremely significantly positive correlation between extracellular resistance and relaxation time. For variety B, C, D, there is significantly negative correlation between extracellular resistance and distribution coefficient of the relaxation time. For variety A, E, there is significantly positive correlation between intracellular resistance and distribution coefficient of the relaxation time. There is significantly negative correlation or extremely significantly negative correlation between intracellular resistance and CAT except variety C. 4 The effect of solution stress of heavy metal ions on electrical impedance spectroscopy parameters of wheat leavesFour electrical impedance spectroscopy parameters are provided with extremely significant difference between different heavy metal ions, concentration of ions, time and interaction of heavy metal ions and time. Distribution coefficient of the relaxation time doesn't show significant difference between interaction of heavy metal ions and concentration of ions or interaction of concentration of ions and time. But the other electrical impedance parameters behave significant difference or extremely significant difference.Comparing electrical impedance spectroscopy parameters under 6 heavy metal stress, for extracellular resistance:Ni2+>Pb2+>Cr3+>Cu2+>Zn2+>Cr6+ , for intracellular resistance: Zn2+>Pb2+>Cr3+>Cr6+>Cu2+>Ni2+,for relaxation time: Zn2+>Pb2+>Cr6+>Cr3+>Cu2+>Ni2+,for distribution coefficient of the relaxation time: Cu2+>Ni2+>Cr3+>Pb2+>Cr6+>Zn2+. There is significant difference between Zn2+, Pb2+, Cr3+ and Ni2+ for relaxation time. The variation of relaxation time is in accord with physiological parameters comparatively (But relaxation time of Cr6+ is not least, cause of which is to be found in the following research), which can be reflected the effect of heavy metal ions stress on wheat leaves.For the six heavy metal ions, there is significantly positive correlation between intracellular resistance and distribution coefficient of the relaxation time. For Zn2+, Cr3+, Cr6+, there is significantly negative correlation between relaxation time and distribution coefficient of the relaxation time. There is significantly positive correlation or extremely significantly positive correlation between intracellular resistance and POD for the six heavy metal ions. There is significantly positive correlation or extremely significantly positive correlation between distribution coefficient of the relaxation time and POD except Cr6+. The effect of Ni2+and Cr6+ on physiological characters is great and that of Zn2+ is little.5 The effect of heavy metal ions stress of soil on electrical impedance spectroscopy parameters of wheat leaves Four electrical impedance spectroscopy parameters are provided with significant difference or extremely significant difference among heavy metal ions or concentration of ions.Comparing electrical impedance spectroscopy parameters in 6 heavy metal stress, for extracellular resistance: Cu2+>Ni2+>Zn2+>Pb2+>Cr6>Cr3+ , for intracellular resistance: Cr3+>Cr6+>Ni2+>Pb2+>Zn2+>Cu2+, for relaxation time: Cu2+>Zn2+>Pb2+>Ni2+>Cr6+>Cr3+, for distribution coefficient of the relaxation time: Cr3+>Ni2+>Cr6+>Pb2+>Zn2+>Cu2+.There is significantly positive correlation or extremely significantly positive correlation between intracellular resistance and distribution coefficient of the relaxation time except Cr6+. There is significantly negative correlation or extremely significantly negative correlation between intracellular resistance and relaxation time except Cu2+, Cr6+. There is significantly negative correlation or extremely significantly negative correlation between relaxation time and distribution coefficient of the relaxation time except Cu2+, Cr6+.The variation of relaxation time is in accord with physiological parameters comparatively (But relaxation time of Cu2+, not Zn2+ is most and relaxation time of Cr3+, not Cr6+ is least .Cause of that is to be found in the following research), which can be reflected the effect of heavy metal ions stress on wheat leaves.6 The effect of salinity stress on electrical impedance spectroscopy parameters of wheat leavesFour electrical impedance spectroscopy parameters are provided with extremely significant difference in time and show extremely significant difference in concentration except intracellular resistance.Along with NaCl concentration and time increased, extracellular resistance and relaxation time of wheat leaves increase firstly and then decrease or decrease gradually. The variation is acute when stress time is less than 12h or concentration of NaCl is lower than 100 mmol·L-1. Intracellular resistance and the distribution coefficient of relaxation time decrease firstly and then increase. The variation for the distribution coefficient of relaxation time appears acute in the range from 0 mmol·L-1 to 50mmol·L-1 or 0h to 12h.There is extremely positive correlation between extracellular resistance and relaxation time. There is extremely negative correlation between extracellular resistance and distribution coefficient of the relaxation time. There is significantly negative correlation between relaxation time and distribution coefficient of the relaxation time.7 The effect of low temperature stress on electrical impedance spectroscopy parameters of wheat leavesElectrical impedance spectroscopy parameters are provided with extremely significant difference in temperature except intracellular resistance, which behaves significant difference. Along with temperature decreased, extracellular resistance, relaxation time and the distribution coefficient of relaxation time decrease gradually. The variations of them are acute between–12℃and -18℃. Intracellular resistance decreases firstly and then increases.The variation of extracellular resistance of wheat leaves can be fitted well with logistic function. After fitting, frost hardiness of wheat leaves calculated with extracellular resistance is -14.10℃. It approaches frost hardiness of wheat leaves calculated with REL(-14.43℃) and the difference is only 0.33℃.Therefore, extracellular resistance is the fittest parameter to determine frost hardiness of wheat leaves after controlled freezing. This result is accord with the reported references.There is significantly positive correlation between extracellular resistance and relaxation time, distribution coefficient of the relaxation time. There is significantly negative correlation between intracellular resistance and relaxation time, the distribution coefficient of relaxation time. There is significantly positive correlation between relaxation time and the distribution coefficient of relaxation time.Above results suggested it is feasible to estimate frost hardiness of wheat leaves by electrical impedance spectroscopy.
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