Postharvest light and temperature elicitors improve chemical composition and level of essential oils in basil (Ocimum basilicum L.) through boosting antioxidant machinery

Abstract

Improving essential oils (EO) quality together with increasing EO quantity has practical significance in aromatic plant industry. In the present study, the effect of postharvest application of light and temperature elicitors including different light intensities [(0, 75, 150, and 300 µmol m−2 s−1) for 24 and 48 h during cold storage (LC), and (0, 250, 500, and 1000 µmol m−2 s−1) during storage at 24 °C for 10 h (L)], UV-C irradiation [3, 6, and 9 h (U)] and 35 °C [3 and 6 h (H)], were evaluated on the photosynthetic performance, physiological and phytochemical characteristics of basil. In general, light elicitors decreased photosynthetic functionality of basil leaves, this negative impact was more detectable when light intensities applied under cold conditions Although soluble carbohydrates increased by different light intensities at 4 °C conditions, co-exposure to light intensities and 4 °C for 24 and 48 h caused a decrease in protein content. Light and temperature elicitors imposed oxidative stress, while boosted antioxidant system in basil leaves. Catalase (CAT) and peroxidase (POX) activity was increased by 300 µmol m−2 s−1 for 24 and 48 h at 4 °C. Light and temperature elicitor applications increased the total phenolic content (TPC) of basil leaves. Concentration of flavonoids increased by elicitors except in the case of 35 °C for 3 h. The total antioxidant capacity (TAC) increased by UV-C irradiation for 3 and 6 h. Abiotic elicitors increased the percentage of EOs content and caused alteration in the chemical composition of EO. Maximum percentage of EO was detected in plants exposed to UV-C (6 h) and 75 µmol m−2 s−1 for 48 h at 4 °C. A significant positive correlation was found between CAT with POX also TPC with TAC in harvested plants under abiotic elicitors. In conclusion, the content of EO and antioxidant activity of basil were affected by the dose and duration of postharvest elicitors. Abiotic elicitors induced oxidative stress and in response, basil boosted the antioxidant machinery, which resulted in enhancement of EO content at postharvest period. Postharvest application of elicitors presents a simple and an effective method, for improving the production of basil EO.