Mg2+
constituent of chlorophyll and therefore essential for photosynthesis.
Fe2+
Constituent of haemoglobin, which transports oxygen in red blood cells
NO3+
Nitrogen derived from nitrate is needed for making nucleotides, including ATP, DNA and RNA. Nitrogen is also needed for amino acid formation.
PO4^3+.
Used for making nucleotides, including ATP, DNA and RNA. A constituent of phospholipids found in biological membranes. Hardens bones.
Ca2+
hardens bones and teeth. also a constituent of plant cell walls