Influence of sulfur and nitrogen supply on growth, nutrient status and concentration of benzyl-isothiocyanate in cress (Lepidium sativum L.)

BACKGROUND: The supply of nitrogen (N) and sulfur (S) exerts an interactive effect on glucosinolate (GS) accumulation in Brassica vegetables, but the consequences for the concentration of isothiocyanates (ITCs), released after decomposition of GS by myrosinase, have rarely been investigated. In addition to their phytosanitary function GS have also been discussed as transient S reservoir.RESULTS: Cress (Lepidium sativum, L.) plants were cultivated with varied supply of N (0.5, 1.0 and 2.0 g pot⁻¹) and S (0, 0.05 and 0.2 g pot⁻¹). Concentrations of total N and S and hence the N/S ratio responded significantly, as did the concentrations of nitrate and sulfate. Concentrations of benzyl-ITC, derived from glucotropaeolin (benzyl-GS), ranged from 6.7 to almost 30 μmol (g dry matter)⁻¹ and were negatively affected by high N supply. For a given S supply the benzyl-ITC concentration was inversely related to the N/S ratio, an indicator of the S nutritional status.CONCLUSION: The results do not support the view that GS act as a transient S reservoir. Rather, moderate N and adequate S supplies lead to increased concentrations of this pharmacologically important constituent of cress.