Zinc is essential for all organisms. It is a group II b metal, with a completed d subshell and two additional s electrons. Thus, unlike other cationic micronutrients, it has only one oxidation state (Zn2+). Zinc plays a structural as well as functional role in plants. It forms a structural component of a large number of proteins with catalytic or regulatory functions. Usually, the Zn2+ ion binds to nitrogen or sulphur-containing ligands through ionic bonds, forming a tetrahedral geometry. Over three hundred enzymes are known to contain Zn as a cofactor (Valee and Auld, 1990). By providing stability to many regulatory proteins, or domains thereof (zinc fingers, zinc clusters and RING finger domains), zinc plays a role in transcriptional regulation (Coleman, 1992). Zinc may chelate with polypeptides, synthesized in response to excessive accumulation of heavy metals (including itself), to form metallopolypeptides like phytochelatins and metallothioneins and contribute to tolerance mechanisms against metal hyperaccumulation. Over the years, zinc has been shown to play critical roles in plant reproductive development, prevention of water stress and protection against toxic effects of reactive oxygen species.