Carbohydrate and Lignin Partitioning in Sorghum Stems and Blades
- G. G. McBee and
- F. R. Miller
Declining fossil fuel supplies has stimulated development of alternate energy sources from plant biomass. Sorghum [Sorghum bicolor (L.) Moench] has been recognized as an excellent crop for anaerobic fermentation to methane because of high carbohydrate content of the vegetative biomass. This study was conducted to determine quantities of hemicellulose (HC), cellulose (CL), lignin (LG), and nonstructural carbohydrates (NSC) partitioned between stems and blades of a spectrum of sorghums. Six entries, E35-1, AT✕ 623 ✕ ‘Rio’ (primarily forage types), Giza-114 (biomass type), RT✕432, AT✕623 ✕ RT✕432, and AT✕623 ✕ RT✕430 (grain types), were produced on a Ships clay (very-fine, mixed, thermic Udic Chromustert). Plants were harvested at physiological maturity of the kernels, separated into stem and leaf blade fractions, and analyzed for HC, CL, LG, and NSC. Structural component content ranged from 716 to 516 g kg−1 for stems and 652 to 567 g kg−1 for the blades. Stems contained 12 to 39 g kg−1 more LG than blades across entries. Content of HC in blades exceeded that of stems, whereas CL levels were higher in stems than blades for all entries except E35-1. The ratio of HC/CL ranged from 0.7 to 0.9 in the stems and 1.1 to 1.3 in the blades. Rind and pith of Giza-114, AT✕623 ✕ Rio and AT✕623 ✕ RT✕430 contained more structural components in the rind. The quantity of NSC was 74 to 216 g kg−1 higher in the stems than blades for all entries. Sorghum stems may contain large quantities of NSC and structural components, but blades are low in NSC for purposes of digestion or methanogenesis.
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