Saline Growth Conditions Favour Supercooling and Increase the Freezing Tolerance of Leaves of Barley and Wheat

When young plants o f barley and wheat grown in hydroponic culture were subjected to salt stress, their freezing tolerance increased with increasing severity o f salt stress. Detached leaves from salt-stressed plants also exhibited an increased ability to supercool. Avoidance o f ice for­ mation permitted leaf survival at subzero temperatures which were no longer tolerated when ice nucleation resulted in extracellular freezing. The increased freezing tolerance under salt stress is attributed to osm otic adjustment o f the plants. Increased cellular solute concentra­ tions decrease the extent o f cellular dehydration at freezing temperatures, thereby decreasing mechanical and chemical stresses on biomembranes during freezing and thawing.