THE EFFECT OF COLD AND SUCROSE CONCENTRATION ON ITS UPTAKE AND ON THERESPIRATION RATE OF ISOLATED EMBRYOS OF WINTER-WHEAT

Both at 5-degrees-C and 20-degrees-C the sucrose concentrations betwee n 8-14 % appear to be optimal from the point of view of dry mass accum ulation by the seedling. The metabolic efficiency was also the highest for these concentrations of sucrose. At both temperatures the hydrati on of the seedlings was strongly dependent on sucrose concentration in the nutrient, diminishing, respectively, from about 6 to about 2 and from about 10 to about 2 mg H2O x mg DW-1. Such low values of the seed ling hydration, however, caused only a 10-20 % decrease of their dry w eight. Within the range of the applied sucrose concentration (2-20 %) its beneficial - trophic interaction prevails over the negative - osmo tic interaction.At 5-degrees-C, as compared with 20-degrees-C, a drop in the seedlings hydration was observed, which appears to be the gener al response of plants to low temperature of growth. An analysis of the 24-hour respiration rate of the seedlings when grown at 5-degrees-C s eems to reveal the occurrence of a process requiring additional metabo lic energy and, probably, associated with the vernalization process. A method of leveling the temperature dependent hydration of the seedlin g is proposed to enable the selection of high-temperature control in t he investigations of the biochemical mechanism of frost hardening and vernalization.