Effects of Water Availability on Two Cytotypes of Switchgrass (Panicum virgatum), a Potential Biofuel Crop
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Biofuels are an important step toward independence of fossil fuels and mitigating global warming. Grasses and other non-food crops have great potential if cellulosic ethanol production can be made economically efficient. Switchgrass is particularly well-suited for ethanol production as it has potential to grow in marginal land, i.e. land where little to no profit can be made from growing other crops. There are two cytotypes of switchgrass (different ploidy-levels) that are suited to different environmnets: Octoploid individuals are suited to upland, dry areas and tetraploid individuals are suited to lowland, wet areas. Tetraploid individuals tend to grow larger than octoploid individuals in their respective environments. We used seven cultivars, or populations, of switchgrass, some native to Michigan and others that are commercially available from around the United States. Under what conditions does each cytotype perform best? Experiment 1: Drought and Rebound in a Greenhouse: Differences in initial mortality rates during simulated drought follow the physiological differences between the two cytotypes, though this difference did not continue throughout the experiment. All cultivars tested showed resilience to drought in early stages, showing some potential for cultivating switchgrass on marginal land. Experiment 2: Water Availability in a Field: There was greater biomass production in tetraploid than in octoploid individuals with high water availability, suggesting tetraploid plants do better under optimal conditions. The interaction between ploidy-level and treatment was expected as tetraploid plants are suited to wetter environments and consequently were more affected by lower water availability than octoploid plants, which are adapted to drier environments. The different cultivars performing well in varying environments shows the potential of switchgrass as a biofuel crop.