Oxygen is created, as sugar is needed to be made through light energy and carbon dioxide. When the sugar is completed, the plant gives out oxygen as waste, which we breathe
The plants use up some of their water and sunlight energy that they have collected over the past day or hours. Once they use their energy they have to make more food to survive which takes more energy to gain the energy they lost, which eventually results in a never ending circle till the day they die.
