The electrical impedance spectroscopy of Scots pine needles during cold acclimation.

The electrical impedance spectroscopy (EIS) was applied to current-year needles of Scots pine (Pinus sylvestris L.) in an 8-year provenance field trial in central Finland during frost hardening. The EIS analysis of the needles using a Model-A equivalent circuit indicated a sequence of events in the needles during their cold acclimation. Some of the EIS-parameters referred to maturation phenomena occurring during the pre-hardening phase at the end of the growing season, and some parameters displayed a clear coincidence with the frost hardening itself. Significant differences between provenances were found in several of the Model-A parameters. Extracellular resistance (re) and beta-coefficient decreased in all provenances in the pre-hardening phase in August and until mid-September. In the same phase, both the intracellular resistance (ri) and the cell membrane time constant (taum) first increased and then decreased. According to taum, re and beta there was a clear gradation between provenances in the pre-hardening phase. From the end of September significant differences were found in the intracellular resistance between provenances, corresponding with the differences in their hardening pattern. The dry weight (DW) content of needles increased during the study period but no clear differences were found between the provenances.