The Influence Of Salicylic Acid On Frost Hardiness And Electrical Impedance Spectroscopy Parameters Of Euonymus Japonicus Thunb

Euonymus japonicus Thunb, belonging to Celastraceae, and genus Euonymus, is an evergreen tree species and has been planted extensively in China. It is able to adapt to low temperature, but the frost hardiness (FH) of seedlings is lower. To study the influence of salicylic acid (SA) treatment on the FH and the parameters of electrical impedance spectroscopy (EIS) in Euonymus japonicus Thunb during the hardening, as well as to find the relation between the EIS parameters and the FH, and perfect EIS method for studying FH on plant, the current-year cutting plants of Euonymus japonicus Thunb were SA treated with 0.1, 1.0, 5.0 and 10.0 mmol·L^-1 before the hardening period, and the water was used as control. The FH of stems was assessed by means of the EIS and electrolyte leakage (EL) methods, the FH of leaves was assessed by means of the EIS, EL and visual scoring of damage (VSD) methods, and the FH results measured by different methods were compared. The EIS, dry matter content, solube sugar content, strach content of stems and leaves were assessed. The content of chlorophyll, the activities of Superoxide Dismutase (SOD), the activities of Peroxidase (POD), the content of Malondialdehyde (MDA) and the content of Soluble Protein of leaves were measured.The main results were as follows:1. During frost hardening, the FH of Euonymus japonicus Thunb with each SA treatment showed an increasing tendency. The FH of Euonymus japonicus Thunb with SA treatment was hardier than that of controlled ones, and the optimal concentration of SA was 5.0 mmol·L^-1.2. With the enhancement of the FH, some changes occurred at the EIS parameters in Euonymus japonicus during frost hardening.3. For non-frost-exposed stems, intracellular resistance (ri), resistance r, and relaxation time (Ï„) had high correlation with the FH measured by EL method (R²>0.50). For frost-exposed stems, the FH measured by extracellular resistance (re),Ï„, and ri methods was highly correlated with that measured by EL method (R²=0.73-0.90).4. For non-frost-exposed leaves, intracellular resistance (ri) had correlation with the FH measured by VSD method (R² =0.50). For frost-exposed leaves, the FH measured by re, andÏ„methods was highly correlated with that measured by EL and VSD methods (R²=0.92-0.96).5. During frost hardening, the dry matter content, solube sugar content, and strach content of stems had correlation with some EIS parameters and with the FH of stems measured by all methods (R²>0.50).6. During frost hardening, the dry matter content of leaves correlated with re (R² =0.51); POD activity of leaves with distribution coefficient of relation time (ψ) (R² =0.50); MDA content with resistances r and ri, and Both R² was 0.54; protein content with re (R² =0.51). The dry matter content, solube sugar content, strach content, chlorophyll content, and protein content of leaves had correlation with the FH measured by all methods (R²>0.50). SOD activity, POD activity, and MDA content of leaves had no correlation with the FH (R²<0.50).