The physiological indices affecting parameters of electrical impedance spectroscopy in Pinus bungeana Zucc. needles during frost hardening.

The electrical impedance spectroscopy (EIS) was analyzed to one-year-old needles of Pinus bungeana Zucc.in an 8-year provenance field trial at the Nursery in Beijing Thirteen Tombs with provenances of Mangshan of Beijing, Xiaoyi of Shanxi, and Liangdang of Gansu. The parameters of EIS and 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 content and the content of dry matter in non-frost exposed needles were tested with different provenances. The relations between EIS and physiological parameters were analyzed. The frost hardiness (FH) of needles was measured by means of the visual scoring of damage (VSD) after artificial freezing test. The results showed that: (1) Both the EIS parameters and the physiological parameters changed during frost hardening, and the EIS parameters and some physiological parameters differed significantly in certain stages of frost hardening, especially in the early stage, which was in accordance with the differences of FH in different provenances. (2) The EIS parameters membrane time constant τm and extracellular resistance re correlated negatively with the chlorophyll content (the correlation coefficient r were -0.91 and -0.68, respectively), the β correlated negatively with the dry matter content (r=-0.74), while the intracellular resistance ri and re had positive correlation with the dry matter content (r were 0.69 and 0.58, respectively), as well as the β with the MDA content (r=0.68). (3) The β correlated positively with the FH assessed by the VSD method (r=0.85), whereas the ri and re did negatively (r were -0.79 and -0.66, respectively).