The Effects of Nutritious Conditions of Seedlings on Growth of Transplanted Tobacco : III. Relation of nitrogen contents in tobacco seedlings to their photosynthetic ability

In the previous experiments by the present author, it had been recognized that the nitrogen amounts contained in tobacco seedlings possessed a high correlation to activity of growth after transplanting. The fact suggested that photosynthetic ability, the principal cause of dry matter production, should be affected by the amounts of nitrogen in the seedlings. With a view to studying this point, tobacco seedlings having different levels of nitrogen content were grown, and the photosynthetic ability of them was measured at the growth stages of 9, 9∼10, 10, 11, 12, and 13 leaves during the seedbed period, at the transplanting day and at 6, 13, 20th days after transplanting, respectively. The photosynthetic ability in the seedbed period was lowered as seedlings grew up. The phenomenon may have been caused by the increase of carbohydrates accompanied with lowering density of proteinic nitrogen in the tissues. Throughout the seedbed period and after transplanting, it was recognized that the increase of carbohydrates in tissues strongly and negatively correlated to photosynthetic ability, but on the other hand, the increase of proteinic nitrogen affected positivebly only through the function of increasing active substances in the tissue maintaining its juvelinity. The increase of carbohydrates and lowering of nitrogen levels in the tissues led to physiological decay in photosynthesis. Therefore, it was considered that nitrogen contents of seedlings should be held at high levels in order to avoid physiological decay of tissues throughout the seedbed period, the seedlings recover normal growth after transplanting