Effect of date of seeding of winter wheat upon some physiological changes of the plant during the winter season

1. Changes in the composition of the crown of the wheat seedling were studied during two consecutive winter seasons, 1923-24 and 1924-25. Plants were taken from three dates of seeding test plats. Seedings were made on or close to the following dates: August 15, August 31, September 21, October 6, and October 19. The order of mortality due to winterkilling, from high to low, for three years, 1922 to 1925, was as follows: October 19, October 6, August 12, August 31, and September 21. 2. In general there seemed to be a positive correlation between the total soluble carbohydrate compounds and better dates of seeding or winterhardiness for the year 1923. The September 21 seeding, the best date of seeding, showed in 1923, particularly, the greatest percentage of total sugars as well as total carbohydrate compounds. However, for the two years' results, winterhardiness could not be attributed to the hexose carbohydrate compounds alone. 3. The total nitrogen compounds remained about the same throughout the winter months, being somewhat higher in the young plants than in the older plants. 4. The water-soluble nitrogen and soluble nitrogen which is coagulable by heat increased during the fall months as the temperature decreased. The soluble nitrogen which is coagulable was found to increase with the lowering of the temperature to the freezing point after which it greatly decreased. 5. The percentage of water-soluble nitrogen which is coagulable was greatest for the favorable dates of seeding, before the plants were frozen, but after freezing occurred the coagulable nitrogen was much less for plants from the favorable than from the unfavorable seedings. 6. The plants from the most favorable dates of seeding have a greater capacity of changing the protein nitrogen from a precipitable to a nonprecipitable form.