Copper is a redox-active transition metal. It exists in two oxidation states, cuprous (Cu+) and cupric (Cu2+). The more stable form is cuprous (Cu+). The ability of copper ions to undergo reversible change in oxidation states (Cu+ Cu2+) enable copper to function in cellular oxidation-reduction processes. Like iron, copper provides sites for reaction with molecular oxygen. It has great affinity to combine with organic ligands. Many copper proteins function as enzymes and electron carriers catalyzing oxidationreduction reactions in cellular metabolism. As a constituent of cytochrome c oxidase, copper functions as a terminal component of the mitochondrial electron transport system. The blue copper protein plastocyanin functions as single electron carrier during photosynthetic electron transport. A similar copper protein phytocyanin has been reported from cucumber seeds (Guss et al. 1996). Copper is also involved in the detoxification of superoxide radicals, lignification of plant cell walls and in pollen fertility.