The role of visible light in the growth and development of a plant is well established. The Sun is the source of light energy. The rays of light reach us in the form of electromagnetic radiations. The spectrum of this radiation consists of gamma rays, x rays, ultraviolet rays, visible rays, infrared rays, microwaves and radio waves etc. Ultraviolet radiation is the part of the electromagnetic spectrum between x rays and visible light with wavelength 100 nm to 400 nm. Ultraviolet spectrum accounts for 5% of all solar radiation reaching the earth. The energy of radiation increases as the wavelength gets shorter. UV radiation therefore has much higher energy than visible light, enough to cause severe injury to plants.