THE USE OF A CONDUCTIVITY MEASUREMENT METHOD FOR ASSESSING FREEZING-INJURY I - INFLUENCE OF LEAKAGE TIME, SEGMENT NUMBER, SIZE AND SHAPE INA SAMPLE ON EVALUATION OF THE DEGREE OF INJURY

After a freezing test the freezing injury of rape leaf discs and wheat tiller segments was expressed in values of relative conductivity (R-t ). R-t represents the electrolyte leakage from a sample frozen at temp erature t as a percentage of the total electrolyte content. The values of R-t did not depend on the number of identical segments (discs) in a sample, but on the segment size, and changed during the leakage time . The same effects were found in relative conductivities of unfrozen s amples (R-0) and freezing-killed samples (R-f). The expression of the degree of freezing injury by an index (I-t) eliminated most of the non -freezing effects and made the conductivity method more accurate and l ess time-consuming. The formula is: I-t = (R-t - R-0)/(R-f - R-0). Opt imal segment size and leakage times are discussed with respect to impr ovement of conductivity measurements of freezing injury. (C) 1998 Publ ished by Elsevier Science B.V. All rights reserved.