1. A positive correlation is recognized, on the whole, between the quantity of starch formed in guard cells and the aperture of stoma in the solution of glucose-1-phosphate, but in plants in their habitat, the opening and closing of stoma do not correlate with the quantity of starch formed in guard cells. After these results, it is considered by the author that the opening and closing of stoma is not affected primarily by the formation of starch in guard cells.
2. Starch is formed more easily in guard cells than in mesophyll cells of leaves in the glucose-1-phosphate solution by the plants cultured in a dark room for more than ten days, but in the case of plants in natural conditions, starch is, on the contrary, more easily formed in the mesophyll cells than in guard cells. It is considered that these phenomena were brought about by the change of pH in the guard cells and mesophyll cells of leaves cultured in different conditions.
3. Formation of starch in guard cells in glucose-1-phosphate solution is checked by calcium and potassium ions and the former ion is more active than the latter, but these two ions do not influence upon the activity of phosphorylase in vitro. It is likely that calcium and potassium ions do not act directly on starch formation of phosphorylase, but these ions would change the permeability of cell and the colloidal system of protoplasm in vivo.
4. In general, the starch in guard cells is consumed by respiration in dark room, but in the case that the substratum contains glucose-1-phosphate, the formation of starch in guard cells is promoted in aerobic condition. In anaerobic condition, even when the substratum contains glucose-1-phosphate, starch is not formed in vivo, but in vitro starch is formed aerobically as well as anaerobically. The activity of phosphorylase is checked by KCN in vivo and in vitro, and it is considered in this case that KCN acts directly on phosphorylase than on respiration. From these results, it was tentatively considered that the existence of oxygen is not directly, but indirectly, necessary for the activity of phosphorylase.
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