Relation Between Parameters Of Electrical Impedance Spectroscopy And Frost Hardiness In Pinus Bungeana Stems And Needles During Frost Hardening

Pinus bungeana Zucc. is a kind of evergreen arbor, which is only produced in China, and is an elite cultivar for its beauty and exotic. It has high cold-resistance. During frost hardening (from September 2006 to January 2007), we studied the parameters of electrical impedance spectroscopy (EIS), frost hardiness (FH) and the physiological parameters of one-year-old stems and needles of P. bungeana in an 8-year provenance field trial at Shisanlin Nursery in Beijing with provenances of Mangshan of Beijing, Liangdang of Gansu and Xiaoyi of Shanxi. FH of stems was measured by EIS and electrolyte leakage (EL); FH of needles was measured by EL, visual scoring of damage (VSD) and chlorophyll fluorescence (CF) respectively. The activities of Superoxide Dismutase (SOD), the activities of Peroxidase (POD), the content of Malondialdehyde (MDA), the content of Soluble Protein, the content of Proline, the chlorophyll concentration, the dry weight/fresh weight ratio (DW/FW) as well as the maximum photochemical efficiency of photosystemâ…¡(F_v/F_m) of needles were measured. The aim of the study was to find the changes of EIS parameters, FH and the physiological parameters, and to verify the relation between these parameters of EIS and FH, and between parameters of EIS and those of physiology.The main results are as follows:1. During frost hardening, the FH of each provenance increases sharply. The FH of stems and needles which were measured by EIS, EL, VSD and CF presents similar tendency. But in the end of frost hardening, the FH was underestimated by the EIS than by the other methods. With the enhancement of the FH, some change has taken place at the EIS parameters and electrical impedance spectra of stems and needles.2. For non-frost-exposed stems and needles, the changes in some EIS parameters of the relaxation tiemÏ„₁, specific intracellular r_i and specific extracellular resistance r_e of stems, r_i, r_e andβof needles have same or opposite trend with the FH, and also have displayed a high correlation with FH which were measured by EIS, EL, VSD and CF (R²=0.51-0.86). After controlled freezing tests, r_e andÏ„_m have displayed a high correlation with FH (R²>0.81). T_m was more close to EL than r_e in measuring FH of needles.3. Relations between the EIS parameters (Ï„_m,βand r_e) and the chlorophyll concentration of non-frost-exposed needles were found during frost hardening(R²=0.51-0.90). The changes in some parameters of EIS had same or opposite trend with that of physiology: for example r_i changed similarly with DW/FW, andβwith the content of MDA; while r_e andÏ„_m varied oppositely with the content of Soluble Protein and the chlorophyll concentration.The FH assessed by r_e andÏ„_m after artificial freezing treatment correlated to the content of MDA (R² = 0.50 and 0.52).4. During frost hardening, DW/FW and r_i increased, and DW/FW also have relations withβ, r_i and r_e (R²=0.50-0.57).5. Relations were found between the F_v/F_m and the EIS parameters (r_e andβ) of the non-frost-exposed needles (R²= 0.68 and 0.55), the FH of the needles which is measured byÏ„_m, r_e and other methods (R²=0.70-0.89).6. The EIS is one of the promising methods for assessing FH, especially without employing a controlled freezing test.