Effects of Photoperiod and Kind of Supplemental Light on Growth and Reproduction of Several Varieties of Wheat and Barley

Six varieties of wheat and four varieties and two lines of barley were grown on 12- or 16-hour photoperiods, each involving nearly 12 hours of natural light plus sufficient artificial light to complete the treatment. The artificial light was obtained from 40-watt fluorescent lamps or from 100-watt incandescent lamps with white, dark-blue, or ruby-red envelopes. 2. In general, most rapid spike emergence of wheat and awn emergence of barley were obtained on 16-hour photoperiods when white incandescent lamps were used as a source of supplemental light. Slowest spike and awn emergence occurred on 12-hour photoperiods with supplemental light from blue incandescent lamps. The white and ruby-red incandescent lamps were almost equally effective in controlling stem length, number of grains per spike, and weight of grains. The fluorescent lamps, while generally less effective than white or ruby-red incandescent ones, provided better control of the reproductive processes than did the blue incandescent lamps.