The important roles played by Zinc are as follow. 
1. In flowering plants such as cotton, chilly, brinjal, paddy, wheat etc as a source of Tryptophan which is a precursor of endogenous plant hormones Alfa Napthalene Acetic Acid(ANNA) produced in the plant body. This hormone plays a very important role in setting of flowers, elongation of secondary and tertiary branches in the grape bunches, which in turn helps in the free development of berries to their maximum size. 

2. Zinc also helps in keeping the leaves of paddy and wheat green, even after flowering and seed setting which in turn increases 1000 gms weight of grains, resulting in increased yield. 
3. Zinc-treated plants become healthy and resist diseases. 
4. Zinc also contributes towards the chlorophyll synthesis and thereby increases photosynthesis activity. 
5. Zinc is essential to plant cell for oxidation reaction, carbohydrate metabolism, sugar usage and formation of growth promoting compounds like Auxin.