SALT CONCENTRATION AND REVERSIBILITY OF ICE-FORMATION AS RELATED TO THE HARDINESS OF WINTER WHEAT

Abstract

Withdrawal of water by ice-formation was not a fully reversible process in the wheat crowns used in this study. However, as the plants became more hardy, the process became more nearly reversible. The water left unfrozen at[long dash]7[degree]C is much greater than can be explained on an osmotic basis from computations from the freezing-point depression of the boiled, expressed juice. At[long dash]13[degree] C the excess unfrozen water is considerably smaller. That is, freezing at the lower temp. appeared to "unbind" the "bound" water. As the season advanced and the plants became more hardy, the soluble mineral content of the tissues decreased in all 4 vars. The concn. of soluble salts in the unfrozen water decreased markedly, since the amt. of unfrozen water tends to increase as hardiness increases. There was a higher salt concn. in the unfrozen water of the tender varieties than of the hardy ones. In 35 winter wheat vars. studied, there was found a considerable inverse correlation between hardiness and soluble salts. In general, hardiness was associated with a high % of dry matter, and with low concn. of soluble salts.