I thought was a good question so I researched and this is the best info I found in couple minutes...curious minds want to know... 

Introduction to Infrared Light in Cannabis Cultivation

Infrared or IR light is electromagnetic radiation invisible to the human eye but can be felt as heat. It occupies the wavelengths just below red light on the electromagnetic spectrum and is crucial for plant growth and development.

In cannabis cultivation, IR light is often overshadowed by other types of light, such as ultraviolet (UV) and blue light. However, it plays a significant role in promoting healthy cannabis growth and increasing yields.

IR light is essential for photomorphogenesis, which influences how plants grow and develop in response to different wavelengths of light. Photomorphogenesis is a critical aspect of cannabis cultivation, as it affects the plant’s growth, flowering, and overall health. 

Infrared (IR) Light: The Dark Horse of the Cannabis Light Spectrum

https://theseedconnect.com/blog/infrared-ir-light/