抄録
In this paper, we report a measurement method of photosynthesis activity for water plants. In the photosynthesis process, the plants absorb carbon dioxide (CO_2) and release carbohydrates and oxygen. The pH value of the water containing plants surely fluctuates through photosynthetic process. As CO_2 is readily soluble in water and decrease pH values, the pH value could be reflect photosynthesis and respiration of the water plants. To quantify the small changes of the pH values, we applied automatic pH measurement system consisting of ion-sensitive field effect transistor (ISFET) sensor that we have previously reported. The pH value in the test tank containing a water plant, cabomba caroliniana, increased 0.840 pH after 4 hours light irradiation. The result indicates that the CO_2 absorption of the plant during photosynthesis could be referred by the pH measurement.
