Magnesium is required in leaves, growing areas of root and stem protein synthesis hence, withdrawn from ageing. It is constituent of chlorophyll, middle lamella, and connected with phosphate transfer in respiration, binding of ribosomes and DNA and RNA synthesis.
Manganese activates enzymes of respiration, photosynthesis and nitrogen metabolism performing oxidation, reduction, decarboxylation, photolysis of water etc.
Copper is activator of plastocyanin, cytochrome oxidase, RuBP carboxylase and many other enzymes. It functions in electron transfer, maintenance of carbohydrate/nitrogen balance, chlorophyll synthesis etc.
Calcium is constituent of middle lamella, activator of enzymes connected with chromosome formation and many aspects of metabolism.