It is important because plants respond to light depend, logically enough, on the plant's ability to sense light. Phototropism is a directional response that allows plants to grow towards, or in some cases away from, a source of light. Photoperiodism is the regulation of physiology or development in response to day length.
Plants absorb carbon dioxide (CO2) and release oxygen for humans and animals to breathe in. Afterward, they'll release CO2 for plants to absorb, which forms a cycle.
