DECREASING HARDINESS OF WINTER WHEAT IN RELATION TO PHOTOSYNTHESIS, DEFOLIATION, AND WINTER INJURY

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Abstract
Pots of 2 vars. of winter wheat were brought into the greenhouse from the field at monthly intervals during the winter. The condition of winter-hardiness of the plants was determined (by the freezing-exosmosis method of Dexter, et al.) when they were brought in, and after 2 and 7 days in the greenhouse. The condition of hardiness was correlated with the vegetative condition of the plants, with the opportunity for photosynthesis in the field, with the defoliation and winter injury due to cold weather, and with growth in the field and in the greenhouse. Conditions which appeared to tend toward a decrease in the concentration of organic food reserves in the plants caused a lessening of their winter-hardiness; higher temperatures, as such, even without appreciable growth, appeared to cause a large decrease in ability to withstand frost injury.