water enters a plant through the plant's roots they suck up the water so the plant can grow. when we breathe air we blow out carbon dioxide the plants breathe in the carbon dioxide and blows out the air we breathe. in the chloroplasts which is a cell in the plant that starts the process of photosynthesis. sunlight is important in photosynthesis because photosynthesis is the process of turning sunlight into food. oxygen is removed from a plant by the little holes in the leaf.