Abstract
Increase in freezing tolerance of winter cereals during cold hardening (1st- and 2nd-phase) is associated with accumulation of compatible solutes. To understand the cryoprotective mechanisms of compatible solutes in the cold hardening process, we determined the subcellular localization of compatible solutes in leaves of winter and spring wheat cultivars. After separation of leaves into subcellular compartments using a nonaqueous fractionation technique, subcellular concentrations of compatible solutes were calculated with the volume of each organelle which was determined using electron microscopy. The results revealed that (1) compatible solute concentrations were changed dramatically when plants were subjected to both the 1st- and 2nd-phase hardening, (2) there was the largest accumulation of all compatible solutes in cytosol, and (3) accumulation patterns of compatible solutes were different in two wheat cultivars. The relationship between changes in freezing tolerance and concentrations of compatible solutes in each organelle will be discussed. (Supported partly by BRAIN.)
