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Abstract
A hydroponic experiment was conducted to study the effects of fertilization with different nitrate/glycine (Gly) ratios on spinach growth and composition of amino acids. Results showed partly replacing nitrate (NO3−) by Gly supplied both nitrogen and carbon nutrition for spinach. Spinach accumulated the equal biomass. Total nitrogen (N) in plant had a positive relationship with nitrate/Gly ratios in nutrition. There was more than 2-fold increase in N uptake from all glycine to nitrate, and plant nitrate contents increased from 0.97 to 3.13 mg g−1. All of 17 proteogenic amino acids in mature leaves exhibited a similar trend, the content in leaf tissue increased with an increasing ratio of nitrate/Gly, whereas relative change rate differed for each individual amino acid. In principal component analysis (PCA), the first component accounted for 80.5% of the total variance, and the N treatment appeared to be separated by this factor. In self-organizing map (SOM), 17 amino acids were divided into three clusters according to responds to nitrate/Gly ratios.