Richards and Caldwell compare etiolated growth, carbohydrate pools and regrowth efficiency of Agropyron desertorum and Agropyron spicatum.A. desertorum consistently produced more regrowth in the absence of photosynthesis than A. spicatum, but a severe preclipping treatment did not significantly reduce etiolated regrowth in either species. Differences in regrowth between and within species were not correlated with crown non-structural carbohydrate concentrations, total pools, or amounts of utilized during regrowth. In uncovered plants, photosynthesis produced most of the carbon required for regrowth after defoliation while carbon for dark regrowth came from total non-structural carbohydrate (TNC) pools and other non-photosynthetic carbon sources such as nitrogenous compounds, organic acids, and structural carbohydrates. Therefore, the authors conclude that A. desertorum is more grazing tolerant than A. spicatum, probably due to it's greater regrowth efficiency and ability to reallocate carbon, and that contrary to popular belief, TNC pools are not the major source of carbon used for plant regrowth after grazing.
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