Zinc is important for proper involvement of several enzymes within plants. When these enzymes aren't being used within the plant, growth and development decreases. Plants that are zinc deficient have far less carbohydrates, proteins, and chlorophyll when compared to plants with a sufficient level of zinc.
"Little leaf" and "rosetta" are the classical symptoms of zinc deficiency in fruit trees. Both these syndromes result from failure of tissues to grow normally. Failure of leaves to expand causes little leaf, and failure of internodes to elongate causes leaves at successive nodes to be so closely telescoped as to give rise to the rossette symptom. In some species, leaves become chlorotic, but in others, leaves may be dark green or blue-green. Leaves may become twisted and necrotic. Flowering and fruiting are much reduced under conditions of severe zinc deficiency, and the entire plant may be stunted.