Location: Grain, Forage, and Bioenergy ResearchTitle: Carbon partitioning into cell wall structural carbohydrates by following 13C label in Switchgrass) Author
Submitted to: Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/30/2011
Publication Date: 2/22/2011
Citation: Soundararajan, M., Sarath, G. 2011. Carbon partitioning into cell wall structural carbohydrates by following 13C label in Switchgrass. Meeting Proceedings of the 2011 International Conference on Bioscience, Biochemistry and Bioinformatics. Pp:296-298 ISBN: 978-1-4244-9388-3. Interpretive Summary: Switchgrass is an important bioenergy species, with the potential to supply high-value biomass from marginal lands. There are different cultivars of switchgrass with varying yield potential and biomass quality. All plants produce biomass through photosynthesis. Using a stable isotope of carbon (13C) as carbon dioxide, it is possible to enrich plants with this 13C-label. Once labeled, it becomes possible to track the change in the amounts of 13C in different plant tissues over time. These types of studies are invaluable in understanding carbon partitioning within the different plant tissues such as leaves and stover, and allow an analysis of carbon distribution and differences between different cultivars. Similarly, a study of key enzymes involved in cell wall biosynthesis can also help identify the process of wall thickening in different plant tissues and provide indicators for potential differences in the quality of biomass. In this study we have used these techniques to understand the difference between two switchgrass cultivars, namely Kanlow and Summer. Our data suggest that Kanlow plants might increase carbon allocation to cellulose relative to summer plants, and that lignification increases gradually in stems relative to leaves. These preliminary data will serve as a foundation for greater in-depth analyses in the future.
Technical Abstract: Carbon isotope ratio analyses of stover tissue from both the lowland (Kanlow) and the upland (Summer) cultivars of switchgrass indicated that the value of Kanlow was less negative (-12.7 per mil.) than the upland variety Summer (-13.1). Preliminary observations on the carbon isotope ratio of cellulose from switchgrass showed a less negative delta 13C value (-12.6) than the leaf carbon isotope ratio (a surrogate for nonstructural carbohydrates) which showed a value of -13.1. Preliminary results from 13C pulse labeling of greenhouse grown switchgrass plants indicated an active partitioning of carbon in their stem tissue over a period of 6 weeks as compared to leaves. Results from further analyses of carbon partitioning into hemicelluloses, celluloses and lignins from stem tissues also indicated an active partitioning of carbon into lignin as the plants mature. Further evidence for an active lignin biosynthesis was also provided by a gradual increase in one of the key enzymes in lignin biosynthesis, cinnamyl alcohol dehydrogenase., in the stem tissue while the same enzyme showed a gradual decrease in its activity in the leaf. Results from this study appear to suggest that an increased carbon partitioning into cellulosic biomass, may necessitate a comprehensive approach to reduce carbon partitioning into the lignin biosynthetic pathway in these plants.