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The effects of drought during preplanting (three treatments: soil relative water content (RWC) 75%–80%, 55%–60%, 35%–40%; B1, 2, and 3, respectively) and postplanting (four treatments: RWC 75%–80%, 55%–60%, 35%–40%, 15%–20%; A1, 2, 3, and 4, respectively) on electrical impedance spectroscopy (EIS) parameters in the stems of Pinus bungeana Zucc. seedlings were investigated by using 4-year-old container seedlings. Stem impedance spectra were modeled by a distributed circuit element model (2-DCE), which showed the extracellular and intracellular resistance (re and ri), relaxation time (τ1 and τ2), and distribution coefficient (ψ1 and ψ2) of relaxation time. After preplanting B3 drought treatment, re and ri increased significantly with the increase of soluble sugar of the stem, measured by enthronlsulphuric acid method. After four weeks postplanting A4 drought treatment, relative conductivity, and soluble sugar of stem increased significantly, and re of stem decreased significantly and continually, indicating that the cell membrane of stem cells was disrupted by severe drought. After five weeks drought treatment, τ1 of stem under A4 treatment decreased significantly, and ψ2 of stem under A2, A3, and A4 treatments was higher than that of A1 treatment. Briefly, drought made re, ri, τ1, and ψ2 of stem change regularly, but re was found to be the most informative and useful parameter measured if used as a single index to assess the drought resistance of P. bungeana Zucc. seedlings. |
