How photosynthesis systems function. Photosynthesis systems function by measuring gas exchange of leaves. Atmospheric carbon dioxide is taken up by leaves in the. The only gas given off during photosynthesis is oxygen. In order for photosynthesis to take place, the plant needs carbon dioxide gas, energy from light and. Mini Lab: What Gas Is Used During Photosynthesis? Objective: To identify the conditions of photosynthesis and the gas used during this process. Best Answer: no. oxygen is produced. in fact carbon dioxide is used in the photosynthesis process to make glucose and oxygen. Gas Exchange in Plants. In order to carry on photosynthesis, green plants need a supply of carbon dioxide and a means of disposing of oxygen. In order to carry on. the gas used by plants during photosynthesis is called carbon dioxide. Photosynthesis. Photosynthesis is the process by which plants, some bacteria and some protistans use the energy from sunlight to produce glucose from carbon. Photosynthesis is a process used by plants and other organisms to convert light energy, normally from the Sun, into chemical energy that can be later released to fuel. Human beings breath in oxygen, and breath out CO2. The plant's leaves, when making photosynthesis, use CO2 and a few other things to make photosynthesis. Photosynthesis. Photosynthesis is a process used by plants in which energy from sunlight is used to convert carbon dioxide and water into molecules needed for growth.