Relationship between parameters of electrical impedance spectroscopy and frost hardiness in stems and needles of Pinus bungeana

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 electrolytic leakage (EL) and compared the regression equations of the two methods in order to optimize the EIS method for studying FH on plants. During frost hardening, EIS and EL were applied to one-year old stems and needles of P. bungeana in an 8-year provenance field trial at the Thirteen Tombs Nursery in Beijing within the provenances of Mangshan of Beijing, Liangdang of Gansu and Xiaoyi of Shanxi provinces, China. A double-DCE model and Model-A were used, respectively, for the EIS analysis of stems and needles that were not exposed to a controlled freezing treatment. After controlled freezing tests, the FH of stems and needles were assessed by EIS and EL. Without controlled freezing tests, the relaxation time (τ1) of stems and the specific intracellular resistance (ri) of stems and needles displayed a statistically significant correlation with FH (R2 = 0.79–0.86); after controlled freezing tests, specific extracellular resistance (re) of the stems and needles, the cell membrane time constant (τm) of needles displayed an even higher correlation with FH (R2 = 0.92–0.94). There were significant relationship between EIS and EL in assessing the FH of stems and needles of P. bungeana, but EIS underestimated FH more than EL did. EIS is one of the more promising methods for assessing FH, especially without employing a controlled freezing test.