For the purpose of making CO_2 absorption by plants realized, we developed a system which can measure and show the change in CO_2 concentration by various plants. The system allows people not only to watch a plant but also to observe CO_2 absorption by it in real time. In addition, this system for the experience exhibit enables them to interact with the plant by using the lights and breathing through the telephone receiver. We exhibited the system on World Exposition Aichi and tested it consecutively. As a result, we confirmed that the system is effective in realizing the activity of plants.