Effect of UV-B elicitation on spearmint’s ( Mentha spicata L.) morpho-physiological traits and secondary metabolites production

Additional artificial ultraviolet-B irradiation (UV-B) is a substitute for the natural UV-B radiation, which is believed to modulate the antioxidants production in plants against the abiotic stress. The present research was formulated by using an indoor UV-B chamber, capable of irradiating UV-B at single wavelength of 315 nm on spearmint. In vitro destructive analysis revealed the reduction in accumulation of chlorophyll a and b as well as carotenoids. However, an elevated levels of phenolic index and total anthocyanins were recorded for both 43.2 KJ/m 2 and 86.4 KJ/m 2 UV-B doses. TBARS assay was carried out to record the lipid peroxidation in the spearmint and likewise, an enhanced secondary metabolites production, an increased lipid peroxidation was seen with the successive increased in the UV–B doses. A remarkable accumulation in the total sugars, reducing sugars and sucrose were also noticed. In vivo analysis revealed a decrease in chlorophyll estimated values as well as an increase of flavanols. Overall leaf fluorescence performance index was improved under both UV-B doses as well as the maximum quantum efficiency of photosystem II. Decreases in the total yield, plant height and length of internode was observed for both UV-B doses however, an enhanced number of stems was recorded for the 43.2 KJ/m 2 UV-B dose. The results of present study not only provided a clear indication of the potential of UV-B in modifying the phytochemicals accumulation in plants but also opened a room for investigating various indoor UV-B doses for future studies of plants and their interaction towards UV-B. Graphical Abstract