The role of sucrose in freezing tolerance in Chrysanthemum cinerariaefolium L-cell cultures.

An efficient procedure using sucrose as cryoprotectant to confer freezing t olerance on high-pyrethrin-producing cell lines of Chrysanthemum cinerariae folium was developed. The efficiency of sucrose depended on both its concen tration in the pregrowth medium and preculture duration. Low sucrose concen tration (90 g l(-1)) induced insufficient dehydration of cells, allowing da mage during intra- and extracellular crystallisation and preventing regrowt h. The high cell dehydration obtained by incubating cells for 10 days in a medium supplemented with 180 g l(-1) sucrose was essential for freezing tol erance but was insufficient to induce cell cryoprotection on its own. At th is concentration, the post-thaw viability rate increased with culture durat ion. 20 days pretreatment afforded a 40 % viability rate, which was correla ted with a 4 and 2.5 times increase in endogenous ABA and sucrose contents respectively. These increase were associated with a different partitioning of water into unfrozen and frozen fractions without modifications in cell d ehydration.