The Reclusive Internodes of Prairie Cordgrass: Tip of the Potential Biomass Iceberg.

Prairie cordgrass (Spartina pectinata) is a leading native perennial candidate for sustainable cellulosic biomass production on poorly drained saline soil in the Midwest and northern Great Plains, having higher biomass yield than switchgrass or Miscanthus on land with drainage and salinity issues. Unlike switchgrass and Miscanthus, this species is highly rhizomatous and its growth habit changes abruptly as sod develops. This change is notably a large reduction in the aboveground internode component. However, number of aerial phytomers is constant. Objectives of this study were to quantify changes in sward structure, tiller morphology, and biomass partitioning between leaf and stem with increasing age of sward. By the third production year >90% of the tillers are vegetative, with very little internode development. For such tillers, internodes of the lower 2-4 phytomers are <1 cm long. Internode elongation does not take place until the 3^rd or 4^th phytomer. Acrotpelly, 2-3 more internodes may partially elongate, while leaves develop normally. These tillers may develop large rhizomes, thus the majority of the stem fraction is belowground. Thus, belowground biomass often exceeds that aboveground, which is composed almost entirely of leaves. Improving sustainable biomass production in prairie cordgrass will require increasing the internode component in aerial phytomers.