Abstract
Sorghum [Sorghum bicolor (L.) Moench] has been gaining attention as a feedstock for biomass energy production. While it is obvious that nitrogen (N) supply significantly affects sorghum growth and biomass accumulation, our knowledge is still limited regarding the effect of N on the biomass quality of sorghum, such as the contents and structures of lignin and other cell wall components. Therefore, in this study, we investigated the effects of N supply on the structure and composition of sorghum cell walls. The cell walls of hydroponically cultured sorghum seedlings grown under sufficient or deficient N conditions were analyzed using chemical, two-dimensional nuclear magnetic resonance, gene expression, and immunohistochemical methods. We found that the level of N supply considerably affected the cell wall structure and composition of sorghum seedlings. Limitation of N led to a decrease in the syringyl/guaiacyl lignin unit ratio and an increase in the amount and alteration of tissue distribution of several hemicelluloses, including mixed linkage (1 → 3), (1 → 4)-β-d-glucan, and arabinoxylan. At least some of these cell wall alterations could be associated with changes in gene expression. Nitrogen status is thus one of the factors affecting the cell wall properties of sorghum seedlings.
Highlights
Sorghum [Sorghum bicolor (L.) Moench] has been gaining attention as a feedstock for biomass energy production
Bioenergy is a sector of renewable energy that includes municipal waste, industrial waste, solid biofuels, biogases, and liquid biofuels, and it accounts for approximately 67% of the current renewable energy mix[1]
The lignin aromatic composition was affected by N supply, as there was a 27% decrease in the thioacidolysis-derived syringyl/guaiacyl-type monomer ratio (S/G unit ratio) in low-N plants, with a 48% increase in the G-type monomer composition, as compared to the control plants (Table 1)
Summary
Sorghum [Sorghum bicolor (L.) Moench] has been gaining attention as a feedstock for biomass energy production. While it is obvious that nitrogen (N) supply significantly affects sorghum growth and biomass accumulation, our knowledge is still limited regarding the effect of N on the biomass quality of sorghum, such as the contents and structures of lignin and other cell wall components. Biomass sorghum can produce more than 42 t h a−1 biomass under favorable c onditions[11], which can be utilized for solid biofuel applications such as biopellets or biochar[7,8,9,10] Another advantage of sorghum is its adaptability to adverse conditions, such as drought or salinity[14]. Ferulate is abundant in grass cell walls and is thought to serve as a crosslink among hemicelluloses and between lignin and h emicelluloses[31]
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