The effects of UV radiation on some structural and ultrastructural parameters in pepper (Capsicum longum A.DC.)

The objective of this study was to evaluate the effects on the structure and ultrastructure of pepper plants (Capsicum longum A.DC.) exposed to UV radiation under greenhouse conditions. The plants were grown in a growth chamber under uniform environmental conditions and after 35 days were exposed to UV-A and UV-C radiation for 15 and 8 days, respectively. Changes in root growth were not significant, but shoot growth decreased in UV-R-exposed plants and decreased significantly in UV-C-exposed plants. Leaf area also decreased in UV-R-exposed plants and decreased significantly in UV-C-exposed plants. Root thickness was not affected by UV treatment, but stem and leaf thickness significantly increased in response to UV-A and UV-C treatment. Stomata increased in number and size in UV-R-exposed plants. At the ultrastructural level, chloroplast thylakoids were dilated and starch reduction was observed. UV treatment resulted in the formation of crystals in the peroxisomes of mesophyll cells. The formation of these crystals was due to an increase in catalase activity, which is an antioxidant enzyme. The study shows that pepper plants were sensitive to UV and the findings provide insight into the physiological changes during UV exposure, and indicate this plant was more sensitive to UV-C radiation than to UV-A radiation.