The dynamic of electrolyte content and the ability of pedunculate oak leaves cell membranes to retain electrolytes during senescence in the autumn were determined. Using the method conductometry it was shown that the dynamics of increasing electrolytes leakage during senescence is different in leaves of genotypes with early and late leaf emergence in the spring. It is associated with earlier initiation of leaves senescence of genotypes with early leaves emergence in the spring. Also a trend towards early initiation of senescence of mature trees leaves compared to those of seedlings was observed. Terms of leaves emergence in the spring, leaves senescence and death in the autumn, are specific to different genotypes, but the differences between leaves emergence quantitatively are strong influenced by the temperature regime during the spring. Separation of oak genotypes by the term of leaves emergence in the spring may be objectively achieved by determining the terms of increasing electrolytes leakage during the autumn, a phenomenon that depends on the genotype heredity and is less influenced by the conditions of year, compared with their influence on the terms of leaves appearance in the spring.