Improving basil (Ocimum basilicum L.) essential oil yield following down-regulation of photosynthetic functionality by short-term application of abiotic elicitors

Basil (Ocimum basilicum L.) is a popular medicinal/culinary species with valuable compounds in its chemical profile. It has been well-known that postharvest quality of crops largely determined by their pre-harvest stance. Here, the effects of pre-harvest application of abiotic elicitors including drought (6, 9, and 12 days water-withholding), calcium [50 and 100 mM calcium chloride (Ca)], salicylic acid [0.5 and 1 mM (SA)], and light intensity (0, 250, 500, and 1000 μmol m−2 s−1) were evaluated on the performance of photosynthesis-related activity, physiological, and phytochemical characteristics of basil. Elicitors generally imposed negative effects on maximum-quantum-yield in photosystem II (FV/FM). Although soluble carbohydrates increased by the effect of drought and decreased by the effect of darkness, prolonged drought and darkness suppressed the protein content. Generally, the application of elicitors boosted antioxidant machinery in basil plants. However, total phenolic content (TPC) decreased by the effect of elicitors except for drought treatment. Drought increased phenolic compounds, flavonoids and antioxidant capacity in basil plants. Abiotic elicitors increased basil essential oil (EO) and caused it to change in terms of chemical composition. The highest EO yields were obtained from basils treated with Ca or SA. In conclusion, pre-harvest application of abiotic elicitors imposed stress on photosynthetic machinery, leading to enhancement of antioxidant activity and EO content. Therefore, it presents a simple and effective method for improving production of EO in basil plants.