Relationships Between Bioimpedance Variables and Gene Expression in Lactuca Sativa Exposed to Cold Weather

Abstract

Four sets of 4 week-old Lactuca Sativa plants, each with 30 samples, were subjected to a nocturnal frost simulation by inserting them into an instrumented freezer with internal temperature maintained at a constant value of −2 °C. At time points of 60, 120, 180, 240 min, one after another lettuce sets were removed from the freezer to be tested with an electrical impedance spectroscopy device, built in the laboratory and based on a commercial electronic board in which a cut leaf of each plant was subjected to a 1 to 300 kHz frequency sweep of an alternate current with a constant tension of 1 V. Results showed a progressive and statistically significant reduction of the critical frequency for which the phase angle reached its minimum as the frost time proceeded (−40% after 180 min, P < 0.05), and this was interpreted as the well known tissue damage due to ice crystals occurring both in cytoplasm and extra-cellular fluids. A quadratic regression of the critical frequency versus the concentration of the protein LBD1 has also been found, which was over expressed by the cluster of genes, whose primers are AGCA GAGGTGGTGAATTTGC (LACTLBD1-F) and AGCTGCCTAAATTGGC GTTA (LactLBD1-R), identified as markers of the applied cold stress in the lettuce plants. It was concluded that an easy to use and inexpensive electrical impedance spectroscopy device can give strategic information concerning the damage occurring depending on abiotic/cold weather in the field lettuce.