Mineral nutrient transport in plants

This chapter deals with the absorption and accumulation of mineral nutrient ions by plant cells and with their primary translocation in the plant. The permeability of the phospholipid bilayer of biological membranes to mineral ions is very low. Transport proteins—carriers and channels—embedded in the phospholipid bilayer facilitate the transport of mineral ions across the membranes. Plant cells accumulate all essential mineral ions to higher concentrations than those present in their environment (Table 1). This accumulation is selective, as evidenced by the different accumulation ratios of the ions shown in Table 1. Some questions that arise are: How is passage through the impermeable lipid bilayer accomplished? How is accumulation against the concentration gradient accomplished? How is metabolic energy coupled to such transport? What is the mechanism of selectivity? How is vectorial transport accomplished? These questions are dealt with in the sections that follow.