title: Nitrogen metabolism and seed composition as influenced by glyphosate application in glyphosate-resistant soybean.
abstract: Previous research has demonstrated that glyphosate can affect nitrogen fixation or nitrogen assimilation in soybean. This 2-year field study investigated the effects of glyphosate application of 1.12 and 3.36 kg of ae ha(-1) on nitrogen metabolism and seed composition in glyphosate-resistant (GR) soybean. There was no effect of glyphosate application on nitrogen fixation as measured by acetylene reduction assay, soybean yield, or seed nitrogen content. However, there were significant effects of glyphosate application on nitrogen assimilation, as measured by in vivo nitrate reductase activity (NRA) in leaves, roots, and nodules, especially at high rate. Transiently lower leaf nitrogen or (15)N natural abundance in high glyphosate application soybean supports the inhibition of NRA. With the higher glyphosate application level protein was significantly higher (10.3%) in treated soybean compared to untreated soybean. Inversely, total oil and linolenic acid were lowest at the high glyphosate application rate, but oleic acid was greatest (22%) in treated soybean. These results suggest that nitrate assimilation in GR soybean was more affected than nitrogen fixation by glyphosate application and that glyphosate application may alter nitrogen and carbon metabolism.
authors: Crop Genetics and Production Research Unit, Agricultural Research Service, US Department of Agriculture, 141 Experiment Station Road, Stoneville, Mississippi 38776, USA. nacer.bellaloui@ars.usda.gov
authors: Nacer
authors: N
authors: Bellaloui
authors: Robert M
authors: RM
authors: Zablotowicz
authors: Krishna N
authors: KN
authors: Reddy
authors: Craig A
authors: CA
authors: Abel
mesh_terms: D004351:Drug Resistance / Q000235:genetics*; D005998:Glycine / Q000008:administration & dosage / Q000031:analogs & derivatives*; D050901:Nitrate Reductase / Q000378:metabolism; D009584:Nitrogen / Q000032:analysis / Q000378:metabolism*; D009586:Nitrogen Fixation / Q000187:drug effects; D018515:Plant Leaves / Q000201:enzymology; D018517:Plant Roots / Q000201:enzymology; D018547:Plant Stems / Q000201:enzymology; D030821:Plants, Genetically Modified / Q000187:drug effects*; D053204:Root Nodules, Plant / Q000737:chemistry; D012639:Seeds / Q000737:chemistry*; D013025:Glycine max / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D000097797:Glyphosate
chemical_list: D005998:Glycine; D050901:Nitrate Reductase; D009584:Nitrogen; D000097797:Glyphosate