Effects of Shading and Temperature on Showy Crotalaria (Crotalaria spectabilis)

Showy crotalaria ( Crotalaria spectabilis Roth) was grown in a controlled-environment greenhouse with a day/night temperature of 32/26C at full sunlight and under 40, 60, or 90% shade. Shading significantly reduced height, dry-matter accumulation, leaf production, leaf-area expansion, axillary-branch development, reproductive development, and the partitioning of plant biomass into stems. Shading increased the partitioning of plant biomass into leaves and the leaf area ratio. Constant shading or shading from 0 through 25 days after planting reduced the leaf area duration (LAD) proportionally more than the net assimilation rate (NAR). Shading from 25 to 67 days after planting reduced NAR and LAD equally. In other experiments reducing the day/night temperature below 32/26C significantly reduced plant height, leaf area, and the rate of leaf production. Dry-matter production decreased significantly at temperatures below 29/23C, because of substantial reduction in LAD. Showy crotalaria flowered and produced seed at temperatures ranging from 23/17C to 32/26C. The results indicate that the geographical distribution of showy crotalaria in the United States probably will continue to increase.