EFFECTS OF FREEZE-THAW INJURY ON PARAMETERS OF DISTRIBUTED ELECTRICALCIRCUITS OF STEMS AND NEEDLES OF SCOTS PINE-SEEDLINGS AT DIFFERENT STAGES OF ACCLIMATION

Frost hardening and frost injury of both the stems and needles of Scot s pine (Pinus sylvestris L.) seedlings were studied by electrical impe dance analysis. This impedance analysis was based on equivalent circui ts with distributed circuit elements (DCE). A double-DCE model for ste ms and two single-DCE models for needles provided excellent fit to the experimental impedance data. However, the single-DCE model for needle s which takes into account the asymmetry of the impedance are proved m ore appropriate than the model. Several parameters changed in to frost injury. In stems, extracellular resistance and one relaxation time de creased with increasing damage, whereas intracellular resistance remai ned relatively unchanged. In needles, the overall pattern for extracel lular resistance and relaxation time was similar to that in the stem. Intracellular resistance remained approximately constant in the case o f the symmetric DCE model. During frost hardening, both extracellular and intracellular resistance increased in stems. In needles, extracell ular resistance increased but relaxation time decreased with hardening . The skewness of the impedance spectra in the Cole-Cole plot for need les increased with hardening. The coefficient for distribution of the relaxation time(s) did not change in either stems or needles with fros t hardening but some changes were found with frost damage.