Plants do not use all of the green light. They reflect it. This is why plants appear green. Other sources emit light in special ways. Metallic vapor lamps are quite efficient for high intensity lighting on larger areas.
Fluorescent tubes are the most economical and convenient in limited areas.
In the fluorescent tube, special phosphors become excited as electricity is supplied to them and give off energy in certain wavelengths. Not all are equally efficient, but this would appear to have a practical application, since plants do not use all wavelengths with equal efficiency. To achieve better efficiency in the response of plants to fluorescent light, special tubes have been designed which emit proportionately more blue and red wavelengths of light. The loss in this portion of the spectrum, even though it is slightly efficient has not been compensated by enough increase in the blue-red portion of the spectrum to result in increased plant growth. Critical experiments show that maximum growth of most plants under cool white fluorescent lights will be equivalent to or better than that obtained under the blue-red phosphors.