Low temperature and ultraviolet-B radiation affect chlorophyll content and induce the accumulation of UV-B-absorbing and antioxidant compounds in bell pepper (Capsicum annuum) plants

Low temperature (LT) and ultraviolet-B (UV-B) radiation are abiotic factors that cause plant stress and limit crop production because of their detrimental effects on photosynthetic components. There is evidence of chlorophyll and carotenoid degradation by LT and UV-B radiation, as well as the production of phenolic compounds as defense components against these stress factors; however, there is scarce information about the interactions between LT and UV-B radiation. Therefore, in this study, the contents of chlorophyll, carotenoids, and phenolic compounds were analyzed in response to LT, UV-B radiation and the combination of both (LT + UV-B) in leaves of bell pepper plants. The LT + UV-B condition produced the greater degradation of chlorophyll in the bell pepper leaves and the higher accumulation of carotenoids, chlorogenic acid and the flavonoids apigenin-7-Oglucoside (A-7-G) and luteolin-7-O-glucoside (L-7-G) compared to the LT and UV-B conditions applied separately. UV-B radiation induced a higher total flavonoid concentration than LT, but the highest flavonoid concentration was observed in the leaves exposed to LT + UV-B. The higher accumulation of chlorogenic acid and A-7-G biosynthesis in leaves exposed to LT than control, indicate a higher resistance of plants to UV-B radiation damage because chlorogenic acid and A-7-G both have high UV-B absorbance capacities. However, a higher concentration of L-7-G, respect to A-7-G, in leaves exposed to UV-B and LT + UV-B indicates a higher necessity to quench ROS,because L-7-G has a higher antioxidant capacity than A-7-G. The increment of carotenoid and L-7-G concentrations in bell pepper plants exposed to LT and UV-B radiation stress displayed a high correlation with the raise of total reducing capacity in their leaves.