Chemistry of root exudates and rhizosphere soils of prairie plants

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Abstract
Root exudates may have important effects on microbial growth and nutrient cycling in many ecosystems. We examined exudation patterns of two dominant plants in the shortgrass prairie.Root exudates of mature blue grama plants contained greater amounts of carbohydrates than younger plants, whereas the latter exuded slightly more amino N than the older plants. Axenic seedlings exuded larger amounts of sugars than normal seedlings; however, there was no difference in the amounts of amino N exuded. Among the amino acids exuded by axenic seedlings the levels of proline, methionine, and glutamic acids were higher than those of the other amino acids. The rhizosphere soil of both blue grama and fringed sagewort had more soluble sugars than the nonrhizosphere soil while the latter had more nonsoluble sugars. Both soluble and nonsoluble amino N were in greater concentrations in the nonrhizosphere soil of blue grama and fringed sagewort than in the rhizosphere soil of the same species. Rhizosphere soil of the above two species contained more polyphenols than the nonrhizosphere soil. Trace amounts of terpenes were found only in the soil associated with fringed sagewort.