The condition of the root system affects the quality of seedlings in forestry and horticulture. Previously, the electrical impedance loss factor (δ) and the reverse-flow hydraulic conductance (Kr ) of the roots of Scots pine seedlings were found to increase when assessed a few days after frost damage. How these variables change with time after the root damage is unknown. We arranged an experiment with 1.5-year-old Scots pine seedlings exposed to -5°C or - 30°C, with the control seedlings kept at 3°C. Then, δ and Kr of roots were monitored for 5 weeks in favorable growing conditions. The properties of the roots were observed to be in a dynamic state after the damage. A significant difference in δ was found between the test temperatures -30°C versus -5°C and 3°C (p = 0.004 and p < 0.001, respectively). The clearest effect of freezing injuries on δ of roots was observed in the first measurement 1 week after the freezing test. The temperature significantly affected Kr, too, with a significant difference between the low-temperature treated plants -30°C versus -5°C and control (p < 0.001, respectively). The difference in Kr between -30°C and the other two temperatures increased with time and was the largest in the last samples, taken after 5 weeks. We conclude that the impedance loss factor may detect root damage if the measurements occur early enough after the damage, but a longer time difference (3-5 weeks) is needed according to the reverse-flow hydraulic conductance.
© 2023 The Authors. Physiologia Plantarum published by John Wiley & Sons Ltd on behalf of Scandinavian Plant Physiology Society.