EFFECT OF FROST ON WHEAT AT PROGRESSIVE STAGES OF MATURITY: I. PHYSICAL CHARACTERISTICS OF THE KERNELS
Samples of freshly cut wheat were exposed in freezing chambers, then stook-cured, threshed, and compared with unfrozen check samples, in the seasons 1929, 1930 and 1932, at Edmonton, Alberta. The check samples attained approximately maximum grade and weight per bushel when cut at a stage of maturity represented by a dry matter content ranging in different varieties and seasons from 50 to 60%. The weight per 1000 kernels of Marquis wheat, determined in 1930 only, reached a maximum at the same stage as weight per bushel. Susceptibility to superficial injury by frost continued generally over nearly the whole maturation period. Even 4 degrees of frost (28° F.) frequently caused a cut in grade, while 8, 10 and 14 degrees caused more substantial degradation, often accompanied by some reduction in weight per bushel. Marquis wheat is apparently more susceptible than Garnet, Reward and Red Bobs, to degradation by frost during the maturation period. Grade, being based on external appearance, is more sensitive to frost than are chemical composition and baking quality. Classification of the kernels of Marquis, in 1930, into vitreous, starchy, immature, green, bran frosted and heavily frosted, confirmed the earlier conclusion (2) that only the sound class (vitreous + starchy) has enough relation to grade to be useful as a grading factor. The germination of Garnet was improved by moderate freezing.