Significance of selenium in ameliorating the effects of irrigation deficit via improving photosynthesis efficiency, cell integrity, osmoprotectants, and oil profile of anise crop

Anise is one of the plants with therapeutic potential, which is classified among the most important medicinal plants with interesting biological effects. Its components could be perceived so as "natural" and "safe" alternatives to antibiotics as well as they are applied in different industries such as food and cosmetic purposes. Selenium (Se) is an essential micronutrient, however, its importance to improve oil yield and quality of anise has not been adequately investigated, specifically under drought. Therefore, two successive seasons were conducted to investigate the effect of selenium foliar application upon anise plants under drought stress. Selenium was applied at three different concentrations (0.0 1.0 and 2.0 mM denoted Se-0, Se-1 and Se-2, respectively) along with two levels of crop evapotranspiration (ET): Full irrigation, 100% of ET (FI) and 60% of ET (DI). The promotive effect of combinations of DI x Se1 or Se2 (for Fv/Fm, RWC%, and MSI% in the first season) and DI x Se-2 (for Fv/Fm, and MSI% in the second season) were as similar as FI x Se-2. Compared to the counterpart control treatment (DI x Se-0), the highest increases in total free amino acids (31.5 and 31.6%), total soluble sugars (84.2 and 86.4%) and free proline content (84.2 and 86.4%) were recorded with application of DI x Se-2 practice in both seasons, respectively. Under DI, Se-2 recorded the maximum values of root length, shoot fresh weight and shoot dry weight in the second season. Under drought, the increases in seed yield due to application of Se-1 and Se-2 amounted to 1.72 and 1.62 folds in the 1st season and 1.50 and 1.43 folds in 2nd one, respectively. The most effective practice for improving IWUE was Se(1)x DI in both seasons, followed by Se-2 x DI. Based on the chromatographical detection, the maximum values of Anethole were recorded with FI x Se-2 while L- Linalool has greatly increased with DI x Se-2. In conclusion, the growers in arid and semi-arid zones are advise(d) (t)o use selenium (2.0 mM) in anise fertilization to mitigate the adverse impacts of drought, and keeping crop yield and quality.