Quantification of frost damage in plant tissues by rates of electrolyte leakage.

A method for assessing frost hardiness of plant tissues [using shoots of Picea rubens Sarg. syn P. rubra (Du Roi) Link] has been developed based upon the rate of electrolyte leakage from shoots immersed in distilled water after exposure to a range of freezing treatments. The relationship between conductivity (the electrolyte concentration in solution) and time has been shown to follow an asymptotic curve, which may be represented by a first-order equation: Ct - Co = (Cauto - Co) (1 - e-kt) where Ct is the conductivity at time t, Co is the initial conductivity, Cauto is the conductivity after autoclaving and k is the first-order rate constant (units time-1). The rate of electrolyte leakage (k) varies directly with the extent of tissue damage. In P. rubens a rate of 0.4% h-1 distinguished between shoots which eventually died, and shoots which remained alive. A minimum of 3 conductivity measurements (after 1 day, 5 days and after autoclaving) is required for a reliable estimate of k. This objective, quantitative method of assessing frost hardiness may therefore be used directly to estimate LT50 values within a population