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<oai_dc:dc xmlns:dc="http://purl.org/dc/elements/1.1/" xmlns:oai_dc="http://www.openarchives.org/OAI/2.0/oai_dc/" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://www.openarchives.org/OAI/2.0/oai_dc/ http://www.openarchives.org/OAI/2.0/oai_dc.xsd">
  <dc:contributor>P. Vivin</dc:contributor>
  <dc:contributor>L.A. DeFalco</dc:contributor>
  <dc:contributor>J.R. Seemann</dc:contributor>
  <dc:contributor>R.S. Nowak</dc:contributor>
  <dc:creator>C.K. Yoder</dc:creator>
  <dc:date>2000</dc:date>
  <dc:description>&lt;p&gt;&lt;span&gt;Root growth and physiological responses to elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; were investigated for three important Mojave Desert grasses: the C&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt; perennial &lt;/span&gt;&lt;i&gt;Achnatherum hymenoides&lt;/i&gt;&lt;span&gt;, the C&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt; perennial &lt;/span&gt;&lt;i&gt;Pleuraphis rigida&lt;/i&gt;&lt;span&gt; and the C&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt; annual &lt;/span&gt;&lt;i&gt;Bromus madritensis&lt;/i&gt;&lt;span&gt; ssp. &lt;/span&gt;&lt;i&gt;rubens&lt;/i&gt;&lt;span&gt;. Seeds of each species were grown at ambient (360 μl l&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;) or elevated (1000 μl l&lt;/span&gt;&lt;sup&gt;−1&lt;/sup&gt;&lt;span&gt;) CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; in a glasshouse and harvested at three phenological stages: vegetative, anthesis and seed fill. Because &lt;/span&gt;&lt;i&gt;P. rigida&lt;/i&gt;&lt;span&gt; did not flower during the course of this study, harvests for this species represent three vegetative stages. Primary productivity was increased in both C&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt; grasses in response to elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; (40 and 19% for &lt;/span&gt;&lt;i&gt;A. hymenoides&lt;/i&gt;&lt;span&gt; and &lt;/span&gt;&lt;i&gt;B. rubens&lt;/i&gt;&lt;span&gt;, respectively), but root biomass increased only in the C&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt; perennial grass. Neither above-ground nor below-ground biomass of the C&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt; perennial grass was significantly affected by the CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; treatment. Elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; did not significantly affect root surface area for any species. Total plant nitrogen was also not statistically different between CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;treatments for any species, indicating no enhanced uptake of N under elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;. Physiological uptake capacities for NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt; and NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt; were not affected by the CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; treatment during the second harvest; measurements were not made for the first harvest. However, at the third harvest uptake capacity was significantly decreased in response to elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; for at least one N form in each species. NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt; uptake rates were lower in &lt;/span&gt;&lt;i&gt;A. hymenoides&lt;/i&gt;&lt;span&gt; and &lt;/span&gt;&lt;i&gt;P. rigida&lt;/i&gt;&lt;span&gt;, and NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt; uptake rates were lower in &lt;/span&gt;&lt;i&gt;B. rubens&lt;/i&gt;&lt;span&gt; at elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;. Nitrogen uptake on a whole root-system basis (NO&lt;/span&gt;&lt;sub&gt;3&lt;/sub&gt;&lt;span&gt;+NH&lt;/span&gt;&lt;sub&gt;4&lt;/sub&gt;&lt;span&gt;uptake capacity × root biomass) was influenced positively by elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; only for &lt;/span&gt;&lt;i&gt;A. hymenoides&lt;/i&gt;&lt;span&gt;after anthesis. These results suggest that elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; may result in a competitive advantage for&lt;/span&gt;&lt;i&gt;A. hymenoides&lt;/i&gt;&lt;span&gt; relative to species that do not increase root-system N uptake capacity. Root respiration measurements normalized to 20 °C were not significantly affected by the CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt;treatment. However, specific root respiration was significantly correlated with either root C∶N ratio or root water content when all data per species were included within a simple regression model. The results of this study provide little evidence for up-regulation of root physiology in response to elevated CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; and indicate that root biomass responses to CO&lt;/span&gt;&lt;sub&gt;2&lt;/sub&gt;&lt;span&gt; are species-specific.&lt;/span&gt;&lt;/p&gt;</dc:description>
  <dc:format>application/pdf</dc:format>
  <dc:identifier>10.1046/j.1469-8137.2000.00576.x</dc:identifier>
  <dc:language>en</dc:language>
  <dc:publisher>Wiley</dc:publisher>
  <dc:title>Root growth and function of three Mojave Desert grasses in response to elevated atmospheric CO2 concentration</dc:title>
  <dc:type>article</dc:type>
</oai_dc:dc>