Form and Function of Zinc Plants

Abstract

1. Abstract The essential micronutrient zinc occurs in plants either as a free ion, or as a complex with a variety of low molecular weight compounds. Zinc may also be incorporated as a component of proteins and other macromolecules. As a component of proteins, zinc acts as a functional, structural, or regulatory cofactor of a large number of enzymes. Many of the physiological perturbations resulting from zinc deficiency are associated with the disruption of normal enzyme activity, thus zinc-deficiency induced inhibition of photosynthesis is coincident with a decrease in activity of key photosynthetic enzymes. Zinc deficiency also increases membrane leakiness by inhibiting the activity of enzymes involved in the detoxification of membrane damaging oxygen radicles. Recent evidence suggests that zinc plays a key role in stabilizing RNA and DNA structure, in maintaining the activity of DNA synthesizing enzymes and controlling the activity of RNA degrading enzymes. Thus, zinc may playa role in controlling gene expression. Though our understanding of the function of zinc has increased greatly in the last thirty years, there are still many aspects of zinc metabolism that remain controversial. In the following review we summarize the current knowledge of the physiology of zinc and illustrate areas in which our knowledge remains incomplete.