Increases in nitrate concentrations in the roots of tomato and cucumber following nitrate addition was significant (tomato ANOVA F(3,8) = 25.26, P = 0.0002; cucumber ANOVA F(3,8) = 6.58, P = 0.0149). Following tungstate treatment, a significant increase in nitrate accumulation was observed in tomato [ANOVA F(3,8) = 10.80, P = 0.00347], but not in cucumber [ANOVA F(3,8) = 0.439, P = 0.7310]. Accumulation of nitrate in the presence of tungstate was not affected in tomato, i.e. difference between treated and nontreated plants exposed to nitrate [ANOVA F(3,8) = 1.76, P = 0.2306], but was significantly reduced in cucumber [ANOVA F(3,8) = 11.11, P = 0.00317]. Error bars = se.