Abstract
In the preceeding paper, it has been described that the transition form of foliar sprayed phosphate to other parts of the plant might be in considerable extent as some sugar esters. In this paper the responses of sugars to the transition rate of phosphate are discussed especially when various sugars are applied on leaves together with inorganic phosphate. Water cultured young wheat plants were placed in dark for 48 hours to starve their leaves of sugars, then applied 5% sugar 1/10 M sodium-dihydrogen phosphate aq. (containning 2 micro curie/ml of P-32) on the 2nd leaf of each plant. These plants were again placed in dark for 48 hours to be examined the transition rate of phosphate in dark. Results are shown in table 2. From this, it can be concluded that common fermentable sugars e.g. glucose and fructose are most effective for the transportation of phosphate, and galactose, xylose, maltose, and soluble starch followed in this order. The reasons why fermentable sugars are so effective for increasing phosphate transportation is supposed to be due to the accelerative formation of phosphate esters in the mediation of energy-rich phosphate bond which is originated in respiratory and fermentation systems in leaf cells in the presence of considerable amount of foliar applied inorganic phosphate. Thus a material that can not be utilized in plant leaf as an energy source, seems not to accelerate the transportation of inorganic phosphate, on the contrary utilizable organic acids etc. are to accelerate the reaction. At any rate, assuming that the foliar appied phosphate will diffuse in concentration gradiant accompanied with esterified phosphate, it is not difficult to suppose that such transition rate much exceeds what is induced from inorganic phosphate alone.
