The discs were then blotted dry and submerged in 0.2 M mannitol solution. The electrolytes leaking into the solution were measured using a conductivity meter (340i WTW, Weilheim. Germany) after 2 h at ambient temperature. The total electrolyte content of the samples was determined by freezing the samples at -20 C for 24 h. and subsequent thawing. Electrolyte leakage mea- sured after 2 h of incubation was expressed as a percentage of the total electrolyte leakage