Besides their involvement in signalling, some elements also play crucial physiological roles in plant life. Low concentrations of nutrients such as K+, Na+ and Mg++ also readily stimulate the activity of major enzymes of the glycolytic pathway, namely phos- phofructokinase and pyruvate kinase, which together regulate glycolysis in plant cells (Plaxton, 1996). Os- moregulation, the opening and closure of stomatal guard cells, and daily changes in leaf orientation are controlled by K+ mobility in plant cells (Hsiao and Lauchli, 1986). Individual micronutrients are simil- arly important components of major enzymes, which regulate all biological processes in plants.