Science: Light of Life

Will farms ever move indoors? If the world’s burgeoning population runs short of food, they may have to, and crops may be harvested in great windowless greenhouses, shut off from natural light. Scientists from Sylvania Electric Products Inc. are already preparing a substitute sun. Last week their laboratory at Danvers, Mass., was lit by a new fluorescent tube, its spectrum trimmed to a lavender glow that to plants is the light of life.

Plants that grow in the open waste a large part of the sunlight that hits them. Their leaves look green because they reflect most of the green and yellow light at the center of the visible spectrum. Their chlorophyll absorbs chiefly red and blue light, so only a small part of sunlight’s total energy is used to turn water and carbon dioxide into sugar, cellulose and other materials that plants need for growth.

This waste does not bother the present-day farmer; the sunlight that falls on his fields is free. But commercial florists, whose greenhouses already blaze with artificial light to speed the flowering of their plants, must pay heavily for electric energy, and much of it is wasted on light that plants cannot use. For florists, and for housewives who grow African violets in dark apartments, Sylvania’s special fluorescent lamp, called Gro-Lux, may mean a significantly smaller electric bill.

To plants, the new light seems twice as bright (gives off twice as much usable energy) as it does to humans. Bathed in its lavender glow, leaves look dark blue-green, and Electrical Engineer Joseph Roland Morin, head of the team that developed Gro-Lux, predicts a great future for the off-color plant lamp. Long before it lights up indoor farms, it may be a boon to commercial florists. “In 20 years,” says Morin, “you won’t see any more conventional greenhouses.”