Abstract:

We studied the frost hardiness (FH) in stems and needles of different Pinus bungeana provenances during frost hardening by means of electrical impedance spectroscopy (EIS) and conventional electrolyte leakage (EL), compared the correlation of the two methods, and optimized EIS method for studying FH of plant. The experiment was conducted on three 8yearold provenances (Mangshan of Beijing, Liangdang of Gansu and Xiaoyi of Shanxi) of P.bungeana planted in Shisanlin Nursery of Beijing. During frost hardening, one yearold stems and needles from the provenances were measured respectively with EIS and EL. DoubleDCE model and ModelA were respectively used for the EIS analysis of the stems and the needles that were not exposed to controlled freezing treatment. After controlled freezing tests, the FH of stems and needles were assessed by EIS and EL. Without controlled freezing tests, relaxation time (T₁) of stem, intracellular resistance (r_i) of stems and needles were highly correlated with FH (R²=0.79～0.86), while after controlled freezing tests, extracellular resistance (re) of stems and needles, cell membrane time constant (τ_m) of needles had a high correlation with FH (R²=0.92～0.94). There was a significant linear correlation between EIS and EL in assessing the FH of stems and needles of P.bungeana. However, EIS underestimated FH than EL did. In conclusion, the EIS is one of the feasible methods for assessing FH, especially without employing a controlled freezing test.

Key words: electrical impedance spectroscopy, frost hardiness, relaxation time, intracellular resistance, extracellular resistance, cell membrane time constant