Journal Article Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. Sugars isotopic labeling 142M471B3J Carbon Dioxide Central metabolism N762921K75 Nitrogen Physcomitrium patens Review Soil ammonium toxicity biochemical pathways carbon partitioning caulonema transition central carbon metabolism elevated CO2 ion suppression and enhancement isomer separation liquid chromatography–mass spectrometry metabolic flux analysis metabolic modeling metabolite quantification mixed-mode column chromatography nitrogen assimilation oilseeds plant metabolism sugar signaling