Early‐stage detection of root freezing injuries of Scots pine (Pinus sylvestris L.) seedlings by impedance loss factor and hydraulic conductance

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