1. Effects of different application time of nitrogen from January to April on the vine growth and the flower cluster development were studied with 3-year-old. Delaware grape vines grown in soils in relation to the nitrogen absorption, assimilation and translocation.
2. Well developed flower clusters were found to be fewer on the March or later applied vines than on the January or February applied vines, though no marked difference of berry set existed among treatments. Shoot growth of the late applied vines was very slow in its beginning and at the stage of flower development, but became rapid toward the blooming time as compared with that of the early applied vines.
3. The early applied nitrogen was absorbed soon by rootlets even when the soil temperature was still under 5°C and stored there mainly as protein. It was then, transported up to the buds with the commencement of the bleeding period namely nearly 20 days before bud burst. Thus in the early applied vines the nitrogen content of rootlets began to decrease rapidly, while it increased even after the bud burst in the late applied vines.
4. When the sap which was bled out at the cut end of the basal part of the shoot was analyzed, it contained more inorganic nitrogen in the late applied vines than in the early applied vines.
Moreover, it held less amide, more glutamic acid and less bases of nucleic acid related substances in the former than the latter.