Abstract
In the previous report, the characteristics of nitrogen metabolism of leaves at their respcetive definite positions were studied to make clear the physiological bases of this function of leaves. The present report is concerned to the phosphorus and potassium metabolism of leaves at definite positions on the stem similar to the case of the previous report on nitrogen metabolism. The following results were obtained. (1) The content of phosphorus and potassium in each leaf increases with their growth, reaches a maximum and then decreases. The time when this maximum content is attained, occurs in sequence from lower leaves to upper leaves as in the case of nitrogen. These elements accumulate in lower leaves and then translocate to upper ones. (2) Before ear-forming period, these elements in the upper leaves are kept at a higher level than in the lower ones. After ear-initiation, that difference between the level of these elements in upper leaves and in lower leaves becomes narrower. (3) Leaves 3/0〜5/0 have direct connection with the tillering. The physiological condition under which they play their principal function, is characterized by high nitrogen and low phosphorus content. These leaves die rather at high level of mineral nutrients, so the cause of their death seems to be lack of carbohydrate as energy source. The chief function of these leaves, 3/0〜5/0,seems to be carbon assimilation to support tillering. (4) Leaves 10/0〜12/0 have intimate connection with ripening. The physiological condition under which they play their function is characterized by low nitrogen and high phosphorus level. The function of these leaves seems to be not only carbon assimilation but also the storing of nitrogen and phosphorus for ripening.
