Bar graph showing the slopes of trend lines obtained through plotting metal tolerance to Ni, Co, Zn and Cd for each line against shoot GSH accumulation. Metal tolerance was scored as the percentage of seedlings with normal upright cotyledons (A) or the formation of a root hook (B). Data represent means of slopes (n = 3 for each metal ± SD). Lower case letters (a, b, c and d) represent significantly different means, using the Tukey-Kramer test comparing all pairs (P < 0.05). Fits of the metal tolerance verses GSH plots for Ni, Co, Zn and Cd in shoots, R2 = 0.99, 0.96, 0.98, and 0.99, respectively, and for roots R2 = 1.0, 1.0, 0.98 and 1.0.