Applications of UV-B lighting to increase phenolic accumulation of Alo vera L. plants

Since supplemental UV-B radiation can provide a simple and economical alternative to increase phenolic compounds in plants, we evaluated the dynamic biological responses of Alo vera L. plants to different UV-B doses (10 and 30 kJ m−2 day−1). The experiment was performed on the basis of Completely Randomize Design with 4 independent replications. Under high light conditions (600 µmol m−2 s−1), UV-B radiation at 30 kJ m−2 day−1 caused significant damaging effects in the Alo plants in terms of leaf biomass. This reduction of leaf biomass coupled with lower values of photosynthetic performance index (PIabs) as well as higher levels of malondialdehyde (MDA). However, when plants were grown at 10 kJ, UV-B-induced increase of proline and soluble sugar content was detected in Alo leaves.  In addition, plants treated with 10 kJ m−2 day−1 UVB dose manifested a significant phenol content enhancement compared to control plants. Most importantly, a significant correlation was obtained between accumulation of leaf phenolic compound and their antioxidant potential, when UV-B radiation was applied at 10 kJ. Our data suggest that an improved accumulation of phenolic compounds can be achieved when UV-B radiation is applied at 10 kJ within 21 days. This can be used to apply UV-B radiations to improve the nutritional quality of Alo leaves by increasing accumulation of phenolic compounds, without affecting the efficiency of photosynthetic apparatus.