What did priestley discover about plants?

Joseph Priestley discovered that plants have the ability to purify air by absorbing carbon dioxide and releasing oxygen. In his famous experiments, he showed that a candle burns out in a sealed container, but if a plant is placed in the same container, the candle can burn longer, indicating that the plant was producing oxygen. This work laid the groundwork for understanding photosynthesis and the vital role of plants in maintaining the Earth's atmosphere.