Effect of Nitrogen and Sulfur Supply on Glucosinolates in Brassica campestris ssp. chinensis

Glucosinolates (GSs) are a group of plant secondary metabolites containing abundant nitrogen (N) and sulfur (S) mainly in Brassica and have the beneficial effects on human health including anti-carcinogenic, cholesterol-reducing and other pharmacological effects. The objective of this study was to investigate the effect of different concentrations of N (5, 10, and 20 mmol L−1, denoted by N5, N10 and N20) and S (0.5, 1, and 2 mmol L−1, denoted by S0.5, S1 and S2) on the yield and GSs in pakchoi (Brassica campestris L. ssp. chinensis var. communis) in hydroponics. Results showed that N10 and N20 significantly enhanced the yield compared with N5, however, N20 had a negative effect relative to N10. Only with N10 and N20 low S supply (S0.5) reduced the yield. The concentrations of aliphatic GSs, aromatic GS and total GSs were enhanced by N5 and indolyl GSs were enhanced by N20. S2 enhanced the concentration of individual GS and total GSs. The concentrations of indolyl GSs were maximized in N20S2 treatment, whereas the highest concentrations of aliphatic GSs, aromatic GS and total GSs were found in N5S2 treatment. Effects of N and S on aliphatic GSs were higher than on indolyl GSs. The results suggest that the accumulation of aliphatic GSs and aromatic GS could be enhanced by low N and high S and restricted by high N while that of indolyl GSs could be enhanced by high N and high S.