Abstract
Climate change has become one of the most complicated challenges of the twenty-first century. Water scarcity is a significant threat to food security, and climate change has adversely affected the likelihood of extreme events such as drought. Selenium (Se) has been reported to mitigate abiotic stress effects, such as drought, on various plant species. The purpose of the current study was to observe the effects of foliar-applied Se to minimize the detrimental effects of water-deficient conditions. Therefore, this study was designed to evaluate the exogenous application of Se at various levels (0, 3, 6 and 9 mg L-1) on the growth, physio-biochemical attributes and antioxidant defense system of lettuce plants growing under an irrigation water deficit from 85 +/- 5% (control) to 35 +/- 5% (drought stress). The results revealed that increasing water deficit stress linearly reduced plant growth and biomass by reducing relative water content (19.49%) and chlorophyll contents (23.95%) through increased electrolyte leakage (20.67%). However, foliar-applied Se significantly increased fresh and dry biomass under control and water-stressed conditions. Under drought stress, Se supply increased free proline content and the activities of SOD, POD and CAT in leaf tissues. The exogenous application of Se partly alleviated the effects of drought on lettuce by the upregulation of the antioxidant system and leaf soluble sugars and a simultaneous decrease in electrolyte leakage. This study further suggests that the upregulation of antioxidants and osmoprotectants is positively associated with the drought tolerance of lettuce. In conclusion, the exogenous application of Se (6 mg L-1) has more potential to improve lettuce growth, physiological attributes and modulation of enzymatic antioxidant potential, which can be recommended for use to maximize lettuce productivity and quality in a dry environment. This research provides a promising, technically feasible strategy for mitigating drought stress in order to achieve the Sustainable Development Goals (SDGs) of good health and zero hunger.