The Effects of Ultraviolet C Radiation on Some Physiological Parameters of Aloe vera L

The increase of atmospheric pollutants and depletion of ozone, are subsequently the main causes for the increase of ultraviolet radiation on the earth. In the present research the effect of ultraviolet C (100-280 nm) on the content of some of the biochemical compounds and growth parameters of Aloe vera L. were examined. According to the results, exposure to ultraviolet C decreased both longitudinal and expansion growth, as well as the size of mesophyll layers of aloe leaves, but increased the thickness of cuticle layer. The histochemical methods also showed that phenolic compounds in the cell walls of those plants which were exposed to ultraviolet irradiation were deposited more esterified to the wall polysaccharides rather than being polymerized compared to those of the non-exposed plants. The content of the ultraviolet-absorbing compounds (i.e., anthocyanins and flavonoids) of UV-exposed plants were also changed. Increase of flavonoids and anthocyanins in these plants, may be related to defensive strategy of these compounds against irradiation.