GROWTH OF PLANTS IN ARTIFICIAL LIGHT 
R. B. HARVEY 
(WITH TWO FIGURES) 
The growth of plants in artificial light has been of interest in 
plant physiology because it offers the possibility of controlling the 
quality and intensity of the light, and the duration of the exposure. 
No reliance can be placed upon sunlight, and its quality and 
intensity vary greatly. The writer attacked the problem of growing 
plants in artificial light to gain some idea of the relation of light 
intensity to the formation and equilibrium concentrations of the 
carbohydrates formed in leaves, and to the translocation of these 
substances in light and darkness. 
The problem of producing plants in artificial light is of some eco- 
nomic interest in Minnesota and other such localities, where the 
sunlight is of short duration and low intensity in winter. It is 
difficult to raise plants in the greenhouse in winter in this latitude 
when the sun is at a low angle. Some analyses made on cabbage 
leaves grown in a greenhouse at the University of Minnesota in the 
winter of 1920 show a practical absence of sugars from the leaves. 
Very little growth is produced under such conditions; the plants 
are weak and easily attacked by fungi. 
The ability to grow plants in this climate by substituting 
artificial light for sunlight, or by using artificial light to supplement 
sunlight on dark days, will be of considerable value for plant 
breeders. The progeny of valuable crosses can be carried through 
one or more generations during the winter, and thereby decrease 
the time required to produce a new strain. In breeding for rust 
resistance at Minnesota it has been found difficult to carry biological 
forms of black stem rust of wheat in culture during winter, owing 
to the weakness of the host plants. 
The writer has succeeded in raising a great variety of plants 
from seed to maturity, using artificial illumination entirely. Light 
was obtained from nitrogen-filled tungsten filament (Mazda) 
lamps. The lamps were mounted on the ceiling of basement rooms 
447] [Botanical Gazette, vol. 74 
