Calcium is an important nutrient in plants. Plants require calcium for proper development of roots and shoots.
Zinc is a cofactor of many key enzymes in biochemical pathways. Deficiency of zinc results in reduced crop yield.
Copper is a component of chlorophyll and is thus important in the synthesis of carbohydrates. It is also essential for the formation of plant cell walls.
Sodium is necessary only in small quantities and for some plants only.