All Plants Are Luminous

All green foliage gives off an invisible deep red—almost black—light. This phenomenon is one of the most fundamental processes of life. It is associated closely with the photosynthesis upon which depends all life on earth. This important discovery was made recently by biologists at the Oak Ridge laboratory of the Atomic Energy Commission while studying changes in a chemical known as adenosine triphosphate in plants engaged in photosynthesis, the formation of starches and sugars out of hydrogen from the soil and carbon from the atmosphere in the presence of light. Newly acquired knowledge about the process is paving the way to improved agricultural methods.

The biologists used extracts from the bodies of fireflies which give off a bright light when this chemical—an important source of energy in muscle—is present. Then they found that chloroplasts, the parts of plants most closely associated with the photosynthetic process, also would give off light when mixed with firefly juice and illuminated. They then made the unexpected discovery that living extracts of green plants give off a light of their own without any mixing.

The light given off by the chloroplasts now is believed to be the exact opposite of the first chemical step in photosynthesis. Light absorbed by the chloroplasts forms unstable chemical bonds within the plant. A small fraction of these chemically induced compounds recombine. The energy liberated by this process is trapped by the chlorophyll molecule, which in turn gives off the mysterious light.

It has been established that leaves, if frozen while exposed to illumination, retain their light-producing ability for several months. It also has been found that certain extracts prepared from leaves undergoing exposure to light contain substances which give off a bright light when certain chemicals are added to them.