In what process occurs in the plant organism free oxygen is formed?

In what process occurs in the plant organism free oxygen is formed? How can you prove its formation by a plant? what is the value of oxygen in nature

Oxygen is released during plant photosynthesis. It is a biochemical reaction to release glucose. When one glucose molecule is formed, six oxygen molecules are released. This can be proved experimentally. Place burning candles under two identical glass bells. There should be a plant under one of them. There, the fire will burn out longer, since oxygen is released by the plant and is used in the combustion process. Oxygen is essential for living organisms, as it participates in many processes and is used to form cells.