Micronutrients are essential for plant growth and reproduction. They are key players in many growth processes such as photosynthesis, cell wall structure and plant metabolism. Micronutrients are just as important as macronutrients, they are just needed in smaller quantities. Micronutrients constitute less than 0.5% by weight of plant dry weight. Many micronutrient deficiencies are rarely seen in the field. Of the eight plant-essential micronutrients, four have the largest impact in crop production. They are: boron (B), iron (Fe), manganese (Mn) and zinc (Zn).

Boron (B) is essential in the cell walls of plants where it cross-links large structural carbohydrates. Flower initiation and pollen development also require adequate B. Symptoms of B deficiency are dry, brittle tissue at both the shoots and roots.

Iron (Fe) is used in the synthesis of chlorophyll, the conversion of nitrogen to a plant-usable form and used in photosynthesis and respiration. Iron deficient plants will show interveinal chlorosis in younger leaves and eventually the entire plant.

Manganese (Mn) is required for the production of oxygen in photosynthesis and as an enzyme activator in respiration. Manganese deficiencies will cause interveinal chlorosis in younger leaves.

Zinc (Zn) is the only metal found in all six classes of enzymes which regulates photosynthesis, formation of plant growth regulators and many plants development processes. Zinc deficient plants will show inter-nodal shortening and stunted leaves.

Examples of deficient plants: