Relation between frost hardiness and parameters of electrical impedance spectroscopy in saplings of different development stage of Pinus sylvestris L. var. mongolica Litv. Relation Between Electrical Impedance Spectroscopy Parameters and Frost Hardiness in Shoots of Apple Rootstocks Relation Between Electrical Impedance Spectroscopy Parameters and Frost Hardiness in Shoots of Apple Rootstocks Relation between Electrical Impedance Spectroscopy Parameters and Frost Hardiness in Stems and Needles of Pinus bungeana The Influence of CaCl2 on the Frost Hardiness and Electrical Impedance Parameters in Stems of Ligustrum vicaryi During Hardening