METHOD: Gene assay CONDITIONS: Growth Chamber - 14h light at 20-15C and 4C for cold acclimation METHOD NARR: Plantlets were grown in vitro at 20/15C and at 4C. The plantlets grown at 4C were deacclimated for 3 days at the warmeras collected from 8-day old plantlets of the control culture and those growing at 4C for 0, 2, 4, 6, 8, 10, 12 days (and deacclimated). Freezing tolerance was assessed by lowering temp. in increments of 2C from -1C down to -leachate was measured. Freezing tolerance was expressed as the temp. which caused 50% ion leakage. The mRNA was isolated and observed for changes associated with decreasing temperatures. RESULTS NARR: Most lines were fully. The hardened plants showed more resistance to freezing than the unhardened controls. Deacclimation caused a decrease in resistance compared to hardened, but still more resistant than controls. Many translation products increased ireatment. Three new products appeared in cold acclimated plants. Most of the changes appeared after 2 days at 4C and remained through day 10. AUTHOR EXPLANATION: Fewer changes in translation products of the less resiss are not active in this line. The increase in frost resistance during cold acclimation was correlated with the changes in translatable mRNA.