Assessment of frost damage in mycorrhizal and non-mycorrhizal roots of Scots pine seedlings using classification analysis of their electrical impedance spectra

Abstract

Key message A novel non-destructive method is presented for studying the frost hardiness of roots. Principal component analysis from the electrical impedance spectra revealed differences between freezing temperatures, but no clear differences between the mycorrhizal treatments as regards freezing stress. Abstract We present a novel non-destructive method for the classification of root systems with different degrees of freezing injuries based on the measurement of electrical impedance spectra (EIS). Roots of Scots pine (Pinus sylvestris L.) seedlings, raised in perlite with nutrient solution, were colonized by Hebeloma sp. or Suillus luteus or left non-mycorrhizal, and exposed to a series of low temperatures (5, -5, -12 and -18°C) after cultivation with and without cold acclimation regimes. In EIS measurements, we ran a small-amplitude electric current to the root system at 44 frequencies between 5 Hz and 100 kHz through electrodes set in the stem and in perlite at the bottom of the container. The normalized (Euclidian) electrical impedance spectra were classified using the CLA-FIC-method (CLAss-Featuring Information Compression) that is based on a subspace method with two variants where the longest projection vector defines the sample class. The current delivery through the root system was affected by freezing injuries in the roots. The most remarkable change, indicating the threshold for cold tolerance, took place between -5 and -12°C for non-acclimated and between -12 and -18°C for cold acclimated roots. No difference was found between the mycorrhizal treatments in the response to the freezing temperatures. The results on the effects of both the low-temperature exposure and mycorrhizas agree with freezing damage assessments done by other methods.

Electrical impedance tomography as a tool for phenotyping plant roots

“…Depending on specific growth medium characteristics (for instance, moisture, nutrient content, and salinity) and plant species, roots can exhibit higher electrical impedance than the medium where they grow [12, 13, 20, 21]. Our experiments employ a growth medium with a considerable amount of mobile ions and were carried out at field capacity; hence we hypothesise that medium disruption by the growing root system and associated changes in electrolytes (such as nutrient uptake and formation of depletion zones) [45] are the primary causes for conductivity decrease observed in the EIT systems.…”

“…An alternative to traditional root-study methods are technologies based on the concept that every biological subject has a defined electrical response. Electrical impedance (EI) techniques have been used to study plant properties such as root surface area [12], temperature tolerance [13], physical deterioration and plant growth status [14]. Electrical impedance spectroscopy (EIS) studies of roots have relied heavily on analogous electrical circuit modelling [15].…”

Classification of Wood Chips Using Electrical Impedance Spectroscopy and Machine Learning

“…Low frequency EIS has been used for wood decay, pore distribution and oil content analyses [19,20]. Recent studies include EIS applications for roots and wood-based composites [21,22].…”

Responses of Parameters for Electrical Impedance Spectroscopy and Pressure–Volume Curves to Drought Stress in Pinus bungeana Seedlings

“…EIS has been widely used to reveal the responses of plant tissues to environmental stress, such as cold acclimation [22][23][24], freeze-thaw injury [20], heat [21], salt [25], elevated ozone [19], and flooding [26]. It has also been applied to evaluate growth of intact root system of herbaceous plants [27], tree roots [28,29] and the mycorrhiza colonization [30], as well as the frost damages of roots in small tree seedlings [31]. Recently, single-frequency impedance measurement was used to study plant response to alkaline stress [32].…”