INVESTIGATIONS OF THE HARDINESS OF PLANTS BY MEASUREMENT OF ELECTRICAL CONDUCTIVITY

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Abstract
Samples of green tissue from several sp. selected at intervals throughout the fall and early winter, were frozen in test tubes. After freezing and thawing, the samples were covered with distilled water. Exosmosis of mineral matter occurred, as measured elec-trometrically, and was greater from tender vars. than from hardy ones, with each sp. The specific electrical conductivity of sections (1 cm. long) of alfalfa roots increased greatly as a result of freezing injury. Roots of hardy vars. hardened most promptly at the crown under exposure to cold in the field, but the more deeply buried parts could be hardened by artificial exposure to cold. The specific conductivity of hardened roots of tender vars. was much higher after freezing than that of similar roots of hardy vars. In these ways, it was possible to quickly differentiate the vars. on a hardiness basis.