抄録
As is well known, silicic acid stands not only closely related to phosphoric acid in physiological function for plants, but also it plays a role in the protection of plants from harmful effects due to the excess of nitrogen. In order to determine whether silicic acid exerts influence on sulphuric acid or not, as well as how it affects plants, some series of experiments were carried out in 1935〜1939 with seedlings of barley and rice plants, which were germinated on damp blotting papers and transplanted into culture solution in the celluloid pots of about 1 litre. The culture solution is of the following composition. [table] Its pH value was maintained between 6 and 7 by addimg HCl or NaOH. For examining correlation between silicic acid and sulphuric acid the culture solution was prepared by such a scheme as seen as table II during the course of experiments the solution was renewed every 3〜7 days. [table] The experimental results thus obtained are briefly set forth in the following. 1) Silicic acid exerts a greater deal of influence on the growth of seedlings of the barley and rice plants. In severe winter of 1936 most of seedlings were found withered away in the pots without silicic acid. 2) A dilute solution exercises influence on the growth of seedlings in the early stage better than a concentrate solution. The reverse is true of the later stage. 3) Despite the depression in growth and yield of barley in 1936 according to the decrease in quantity of sulphuric acid, the addition of silicic acid results in filling up the loss. Where adding 30 mg of silicic acid to the pots which are wholly destitute of sulphuric acid, the plants undergo normal development. Beyond doubt silicic acid serves as a substitute for sulphuric acid. 4) In the pots without silicic acid the plants become highly feeble so as to hang down their lower leaves and present larger number of withered leave as compared with those in the pots with silicic acid. Unless silicic acid is added seedlings seem to be incapable of undergoing normal growth in the cold season. 5) The plants in the pots with some quantity of silicic acid exhibit a close resemblance in general appearance of leaves to those in the fields. In the pots with 0.3 mg of silicic acid or entirely wanting, however, the plants are marked with narrower leaves. It may be seen that the leaves broaden as the quantity of silicic acid increases. 6) Notwithstanding the normal growth in the pots with 30 mg or 3 mg of silicic acid, the plants in those with 0.3 mg or entirely devoid of silicic acid exhibit very small brownish blackspots about two weeks after the commencement of experiments, gradually extending from the top of every leaf to its sheath. As the spots increase the leaves assume a yellowish brown colour, bigining from the top, and finally wither away. At a glance these spots in question look like those produced by the attack of a certain plant disease. Through the plant pathological experiment, however, it is made out, clearly that this is not so. To sue it appears that the spots are those physiologically caused by the deficiency of silicic acid.
