ABSTRACT
Summary Establishment of warm-season prairie grasses is often difficult because of slow seedling growth and weed competition. Seedling development of four perennial warm-season grasses was compared with that of a vigorous annual grass, giant foxtail (Setaria faberi Herrm.) Big bluestem (Andropogon gerardii Vitman), switchgrass (Panicum virgatum L.), indiangrass (Sorghastrum nutans [L.] Nash), Caucasian bluestem (Bothriochloa caucasica [Prin.] C.E. Hubb.), and giant foxtail were grown in a greenhouse. Leaf elongation rate, collaring date, and leaf length were measured daily. Carbon-exchange rate (CER) was determined. Plants were harvested at the sixth and eighth leaf stages, and yield components, leaf area, and tiller numbers were recorded. Giant foxtail had a very rapid leaf elongation rate, developed quickly, and had little tillering up to the eighth collared-leaf stage. Big bluestem and Caucasian bluestem developed nearly as quicky as giant foxtail, but leaf elongation rate was much slower, and leaves were shorter. Caucasian bluestem tillered at an early stage and developed additional photosynthetic area, although not much. Big bluestem allocated more of its assimilates to the root system and did not tiller as much as Caucasian bluestem. Switchgrass and indiangrass developed much more slowly. Once they reached the fourth leaf stage, their leaf elongation rate was intermediate between those of giant foxtail and Caucasian or big bluestem. Switchgrass tillered more than big bluestem. Carbon-exchange rate was lower for giant foxtail and Caucasian bluestem than for the other grasses. In a breeding program, selecting for rapid leaf elongation rate in Caucasian bluestem and big bluestem could result in greater seedling vigor since more photosynthetic area would be produced. Switchgrass and indiangrass selected for rapid development prior to the fourth leaf stage with the same or greater leaf elongation rate that occurs later in their development could result in greater seedling vigor. Screening for CER probably would not result in greater seedling vigor.
