Effects of Day Length and Light Intensity on Growth of Barley

The effects of variations in light intensity, photoperiod, and light quality on shoot dry weight, tillering, and leaf growth of barley (cv. Prior) have been examined in controlled environments. The rates of tillering and of dry matter production were primarily dependent upon the total radiant energy incident upon the plants. Tiller-iug was unaffected by changes in the photoperiod (independent of light energy) or in the spectral composition of the light which profoundly affected apical develop-ment. At low light intensities, tiller buds on the main axis only elongated, whereas at higher intensities secondary and higher·order tillers were produced. The largest number of tillers was associated with the coieoptile node, and tiller production declined regularly with each successive node up the main axis.