MORPHOLOGICAL DEVELOPMENT OF SWITCHGRASS AND KLEINGRASS

Accurate and precise measurements of plant maturity are essential in research involving perennial warm-season grasses. The objective of this study was to devise and refine such an index for use with determinate and indeterminate flowering warm-season perennial grasses. An index of 35 separate stages distributed among three major developmental events (leaf, stem, and reproductive development) was devised and tested on switchgrass (Panicum virgatum L., determinate flowering habit) and kleingrass (Panicum coloratum L., indeterminate flowering habit). Switchgrass and kleingrass were sampled in two growth periods, spring and summer of 1989. Switchgrass only was sampled in spring of 1990. At each sampling, 30 to 50 tillers were classified into stages, counted, dried, and weighed. An additional 30 to 50 tillers were separated also into leaf, stem, sheath, and inflorescence (if exserted) fractions. Kleingrass flowered earlier and developed morphologically nearly three times faster than switchgrass in spring 1989 and twice as fast in summer 1989. In 1990 switchgrass exhibited a sigmoidal development pattern with three distinct phases, each with a different rate of development. The phases were related closely to temperature and rainfall patterns with greater rates of development occurring during relatively cool and wet periods. The experimental index described switchgrass and kleingrass development well. Most stages were rapidly and easily recognized. Reproductive stages were sometimes subjective and may have to be revised.