Flowering of bromegrass, Bromus inermis, in the greenhouse as influenced by length of day, temperature, and level of fertility

Greenhouse studies were conducted during two winter seasons to determine the environmental conditions most favorable for normal growth and flowering of smooth bromegrass, Bromus inermis. In the 1944-45 study, no flowering occurred with three clones of bromegrass under normal day length (9 to 10 hours), some flowering occurred with a 15-hour day, and relatively good flowering occurred with an 18-hour day. Early, midseason, and late-maturing clones responded differently to changes in day length, temperature, and level of fertility. In general, panicle production was considerably greater in an early-maturing clone than it was in a midseason clone and in a late-maturing clone studied. With the early-maturing clone, the number of panicles per plant was approximately the same under day lengths of 15 and 18 hours and at temperatures of 65 degrees and 75 degrees F. Panicle emergence however, was delayed both by the shorter day and the lower temperature. With the late-maturing clone, only 60% of the plants flowered with a 15-hour day while all plants flowered with an 18-hour day. All clones responded to a high level of nitrogen, the plants receiving a full nutrient solution producing from 30 to 50% more panicles than those receiving a nitrogen-deficient solution. In the 1944-45 study, Canadian certified commercial and Achenbach, a "southern" variety, were grown at two temperatures and two levels of fertility, with a day length of 18 hours. In general, the Canadian strain flowered more normally than did the Achenbach strain within the range of conditions supplied in this experiment. Vegetative growth was excellent and flowering profuse in plants of the Canadian strain when grown either at 60 degrees or at 80 degrees F in soil of high fertility. In soil of low fertility, vegetative growth was poor, but panicle production still averaged 2.8 per plant as compared with 0.5 per plant for the Achenbach strain under similar conditions. Plants of the Achenbach strain showed a marked response to temperature as well as to soil fertility. Vegetative growth and production of panicles was considerably greater in plants grown at 80 degrees F than in those grown at 60 degrees F, and were much greater in soil of high fertility than in soil of low fertility. In general, plants that flowered well produced adequate seed, if given the opportunity for cross fertilization. It was observed that in the cool house (60 degrees F) on cloudy days little or no anthesis occurred. The data presented suggest that under greenhouse conditions with an 18-hour day length, favorable flowering of Canadian bromegrass may be expected under a fairly wide range of temperature and soil fertility conditions, while for best results with the Achenbach strain, a high level of fertility and a relatively high temperature apparently are needed.