What role does cell membrane surface potential play in ion-plant interactions

Almost all cell membrane surfaces (CMS) are intrinsically negatively charged. These negative charges create a surface electrical potential (φ₀) which affects ion concentrations at the CMS and consequently affects the phytotoxicity of metallic cations and metalloid anions in different ways. The φ₀ is also controlled by the ionic composition of the bulk-phase medium (BM). Common cations, especially H⁺, Ca ²⁺ and Mg²⁺, can reduce the negativity of φ₀ by ionic screening and binding. Treatments that reduce the negativity of φ₀ would reduce the surface activity of Cu ²⁺ ({Cu²⁺}₀) and increase the surface activity of arsenate ({As(V)}₀) at the CMS, and consequently alleviation of Cu²⁺ toxicity but aggravation As toxicity would be expected. It is the φ₀, rather than site-specific competition, that plays the principal role in ionic interactions and biotic effects.