MATHEMATICAL MODEL FOR DESCRIBING THE POST-CRYOPRESERVATION VIABILITY OF FRUIT AND BERRY CUTTINGS

A mathematical model that simplifies the determination of optimal parameters ensuring the maximum viability of frozen-thawed fruit and berry cuttings was developed. Values of the minimum amount of intracellular water η1min, which minimizes the plasmolysis probability, and η2min, which minimizes the probability of intracellular ice formation, were determined with due account for the bioobject heterogeneity. Free water amounts Δη, forming ice crystals inside the cell during cryopreservation of different of fruit and berry varieties, were calculated. The optimal conditions for cutting dehydration (temperature Ti and incubation time t2, minimum amount of intracellular water ηmin) ensuring the maximum viability after drying and low-temperature adaptation to cryopreservation were selected. The individual features of the viability of frozen-thawed cuttings of different species were quantitatively reflected in the free water index Δη. The maximum viability of frozen-thawed birch and blackcurrant cuttings was achieved, when intracellular water was in the bound, vitrified state Δη = 0. The calculated Δη˃0 for cuttings of different varieties of apple- and pear-trees as well as of raspberry-bushes leads to a decrease in the viability, and it is impossible to obtain viable plum, apricot or grape specimens after low-temperature cryopreservation with no bound water ηс at all.