In plants, a small amount of zinc is needed and too much can be toxic. Nuts and peas have more. Zinc can be less available in heavily fertilized soils. When zinc is deficient in corn, tryptophan may be lacking. It may also affect protein formation in other plants, reducing the number of essential amino acids.
Deficiency shows up in younger leaves as stunting or abnormally small leaves.
The area between the veins turns yellow and bronze colored spots form around the margins of the upper leaves. Leaf tissue between veins turns a creamish yellow while area along the veins remains green. Plants have stunted leaves that are curved upwards, looks like leaf roll virus. In general, leaves are smaller, internodes shorter and stems are more rigid. Zinc sulfate can also be mixed with lime or soda ash to form a longer lasting film on leaves.