S. T. Dexter

The Evaluation of Crop Plants for Winter Hardiness

Publisher Summary The chapter describes that the plant breeder, agronomist, or horticulturist, in the evaluation of crop plants for winter hardiness, the physical and chemical changes or properties that accompany winter hardiness should be found easily and reliably and to a greater degree in varieties that are winter-hardy than in those that are not. The studies with refrigeration machines have been made in the plants in the hardened condition have been frozen at specified temperatures. Examination of the injury from freezing has given varietal ratings in close conformity with field experience. The electrical conductivity method of estimating injury has been more and more commonly used, especially in horticultural evaluation, because of its convenience and objectivity. In spite of many complications due to diseases before and after hardening and other similar difficulties, winter hardiness in plants has been shown to be remarkably well correlated with tolerance to low temperatures. The chapter presents several methods that have seemed to have promise, and numerous physiological studies have considerably advanced the knowledge of winter hardiness and the hardening process. The parts of this fundamental research have not been applied or appraised adequately by agronomists; an excellent opportunity exists for the development of new and better methods for the evaluation of the winter hardiness of crop plants.

Specific gravity of different zones within potato tubers

Summary and ConclusionsThe specific gravity of three concentric zones within tubers of 19 potato varieties was determined over the two-year period 1956–1957. During this study, a clear pattern emerged. In varieties where specific gravity of the entire tuber was high there was a large difference in spcific gravity between zone three (pith) and the two outer zones. In varieties with low specific gravity this difference was comparatively small. There was generally little difference in specific gravity between zones one and two. Specific gravity of zone three was relatively uniform between varieties.