COMPARISON OF GRO-LUX AND COOL-WHITE FLUORESCENT LAMPS WITH AND WITHOUT INCANDESCENT AS LIGHT SOURCES USED IN PLANT GROWTH ROOMS FOR GROWTH AND DEVELOPMENT OF TOMATO PLANTS

"Gro-lux" fluorescent lamps, a light source providing high energy in the blue and red regions of the spectrum, were designed and marketed by the Sylvania Company (4) especially for growing plants under artificial light. Their effectiveness for growing tomato plants was compared with that of cool-white fluorescent lamps, with and without adding 35% of the fluorescent wattage as incandescent light. On a percentage basis the dry weights of the stems and leaves after 5 weeks were, cool-white 100%, gro-lux 82, cool-white plus incandescent 131, and gro-lux plus incandescent 153. The addition of incandescent to gro-lux fluorescent as compared with gro-lux alone resulted in 44% increase in root dry weight, 73% increase in leaf area, and 80% increase in plant height. The increased growth obtained under either gro-lux or cool-white when incandescent is added is attributed to an increase in plant height caused by the addition of far-red energy, permitting more light to reach the lower leaves. Plants grown under gro-lux with incandescent had 34% more flowers, 20% more ripe fruit, and 32% heavier fruit than those grown under cool-white with incandescent.