Figure 1.

Relative root elongation (RRL) of wheat (cv. Yecora Rojo) seedlings exposed to toxic levels of Cu²⁺ affected by Ca²⁺, Mg²⁺ and pH. Data were taken from Parker et al. The RRL is plotted as functions of (A) Cu²⁺ activities in the bulk medium, (B) Cu²⁺ ion activities at the CMS_e, (C) calculated Cu²⁺ toxicity based on the electrostatic toxicity model or (D) the ψ₀^o (x-axis) and Cu²⁺ surface activity (y-axis).