Growth and Floral Development of Five Species of Range Grasses in Central Oklahoma

Abstract

Growth and floral development of little bluestem, big bluestem, switch grass, Indian grass, and side-oats grama under prairie conditions were investigated near Norman, Oklahoma during the growing season of 1948. While side-oats grama showed practically no internodal elongation before floral initiation, Indian grass showed the greatest amt. of such elongation. Little bluestem did not show any very definite variations among the different topographic sites. Floral initiation in all spp. proceeded at the greatest rate during the long days of late spring and early summer. Anthesis occurred chiefly during early summer in side-oats grama, but in the other spp. it did not begin until the daylength had decreased a substantial amount below that at the time of floral initiation. Considering the fact that all these spp. have previously been shown to be photoperiodically sensitive, using flowering as a criterion, present data suggest that, with the exception of side-oats grama, either the optimum photoperiod for floral initiation is different from that for flowering in the particular plants observed, or that inflorescence initiation can occur over a greater range of photoperiods than it does under prevailing field conditions. The number of leaves with blades expanded on a given culm was found to be a fairly accurate index of the time of floral initiation in all spp. In all spp. except side-oats grama, there was considerable evidence that culms which do not have the required minimum number of leaves by a certain date remain vegetative. The intervals between inflorescence initiation and exsertion were 43 days in little bluestem, 50 days in big bluestem, 35 days in switch grass, 64 days in Indian grass, and only 15 days in side-oats grama. The time between the start of exsertion in a given culm and anthesis was less than 1 week in little bluestem, big bluestem, and Indian grass, about 4 weeks in switch grass, and 2 weeks in sideoats grama.