As a result of the process of photosynthesis where carbon dioxide and water and used to synthesize glucose, the plant will find itself with extra glucose which is still needed but not at that point.
It will therefore store the glucose in roots, stems and leaves. It will however, convert them to starch first so that they are not affected by osmosis. Starch is not soluble in water which is why osmosis will not affect them and cause they to swell too much which would reduce the space the plant has.
