Assessing frost hardiness of Pinus bungeana shoots and needles by electrical impedance spectroscopy with and without freezing tests

Abstract

Aims Nursery and forest operations require that frost hardiness results be produced faster than can be provided by controlled freezing tests. There is a great challenge to develop a rapid method for predicting frost hardiness that might not necessitate controlled freezing tests. The aim of this study was to examine the assessment of the frost hardiness of shoots and needles of Pinus bungeana by electrical impedance spectroscopy (EIS) with and without controlled exposure to freezing. Methods The frost hardiness of current-year shoots and needles of P. bungeana in an 8-year-old provenance field trial was measured at Shisanlin Nursery in Beijing, China, from September 2006 to January 2007 by means of EIS and conventional electrolyte leakage (EL). In the same plants, but without controlled freezing test, were monitored the EIS parameters in current-year shoots and needles. Important Findings The results showed that (i) after controlled freezing tests, the frost hardiness estimated by EIS parameters (extracellular resistance, re, and membrane time constant, sm) was significantly correlated with the frost hardiness assessed by EL method (r = 0.95) and (ii) for the samples not exposed to controlled freezing treatment, the relaxation time s1 for shoots and b for needles had greater correlations with the frost hardiness estimated by EL after controlled freezing tests relative to the other parameters (r = � 0.90 for shoots and r = 0.84 for needles, respectively). The parameters re of shoots and needles and sm of needles might be applied for measuring frost hardiness of samples after exposed to controlled freezing tests. The frost hardiness results can be obtained within 48 h. The parameters s1 of shoots and b of needles could be used for estimating the frost hardiness of samples without using a controlled freezing test. The frost hardiness results can be obtained within 24 h.