Comparative analysis of metabolites profile in spinach (Spinacia oleracea L.) affected by different concentrations of gly and nitrate

The ability of plants to uptake amino acids has been confirmed by extensive research; however, the subsequent post-uptake metabolism of absorbed amino acids is poorly characterized. With the aim of elucidating the different effects of inorganic and organic nitrogen sources on primary metabolic pathways in spinach, a gas chromatography-mass spectrometry (GC-MS) based metabolic approach was used to identify differentially abundant compounds in spinach (Spinacia oleracea) leaves after 2 days hydroponic culture in one of three concentrations of glycine or nitrate. Principal component analysis (PCA) revealed distinct clusters for different treatments. The first and second components of PCA accounted for 63.6% and 13.6% of total variance, and seemed to be mainly influenced by the nitrogen concentration and amount of Gly input, respectively. Compared to control treatment, most identified metabolites increased in dose-dependent manners as nitrogen availability increased; however, distinct patterns were observed for NO3-- and Gly-treated leaves. When nitrogen was deficient, NO3--treated leaves had lower relative contents of carbohydrates, organic acids and amino acids than Gly treated leaves, this trend reversed under N-sufficient conditions. Furthermore, the metabolites identified were profiled to highlight the overall metabolic shifts between NO3- and Gly as N sources at different concentrations. (C) 2016 Elsevier B.V. All rights reserved.