Evaluation of Light Sources for Plant Growth

Abstract

The relative effectiveness of various sources of light for the growth of plants was evaluated by means of simultaneous determinations of growth rates at 3 intensities of light for each source. The slope of the growth/intensity curve is taken as an index of the light source effectiveness. Sample evaluations were made using 2 species of plants: Knox wheat and Red Kidney bean. Lamp combinations tested include various combinations of incandescent, fluorescent and improved mercury arc lamps. Increases in intensity to 4500 ft. candles (889 watts/16 sq. ft.) yielded continuous increases in growth rates of wheat, but saturated growth curves for bean. The most effective lamp combination was fluorescent plus incandescent.