This program opens with a film of the U.S. Department of Agriculture's Agricultural Research Station in Beltsville, MD. In one greenhouse two groups of plants are receiving the same daytime conditions, but at night one is kept in total darkness while the other receives eight additional hours of incandescent light. Two four-year old loblolly pines show the results of this experiment. Dr. H. A. Borthwick explains that this is to study photoperiodism, or the effect of light on the plants' growth mechanism. In 1918 Wightman W. Garner and Harry A. Allard discovered that it is not the length of the day but rather of the night that is the determining factor in flower and seed production and growth of plants. Further experiments with lettuce, bean, tomato, and corn seeds test the effect of spectrum light colors and exposure on germination. A far red light creates a taller plant, and red light creates the tomato skin color. The mechanism in a plant the reacts to light is not chlorophyll but rather a two-way growth pigment, phytochrome, that acts as a switch with red and far red light. A film shows the process, using a spectrophotometer, by which this was determined. K. H. Norris demonstrates a spectrophotometer with a corn sample and explains the results with graphs. Two film clips show Sterling B. Hendricks doing further research on phytochromes to isolate their molecular structure and Soviet Prime Minister Nikita Khrushchev at Beltsville, MD listening to Dr. Borthwick discuss crop growth issues.