Controls on bud activation and tiller initiation in C3and C4tallgrass prairie grasses: the role of light and nitrogen

Abstract

Population dynamics of perennial grasses in tallgrass prairie ecosystems are strongly influenced by vegetative outgrowth from their belowground bud banks. We examined the role of light and nitrogen in regulating tiller initiation and tested an integrated model of controls on bud dormancy and activation in several C3and C4grasses. In addition, we assessed the interaction of nitrogen and light quantity and red – far red spectral composition on tiller initiation. Belowground perennating organs of three C3and three C4species were grown under full light or dark conditions, amended with one of four nitrogen concentrations (0 to 350 ppm N). Dormant buds were also subjected to full light under different spectral compositions or to continuous darkness. Our results among C3grasses support the integrated model as light and nitrogen played important and interacting roles in the regulation of bud banks. However, differences in responses among C4grasses and a lack of light × nitrogen interactions suggest that an alternative model may be necessary for this functional group. Our results provide predictions of responses to nitrogen enrichment or light imitations in prairie ecosystems due to interacting disturbances such as reduction in fire frequencies, alterations in grazing intensities, or climate change.