Involvement of abscisic acid on antioxidant enzymes activity and gene expression in Lavandula angustifolia cv. Munstead under drought stress

Climate change combined with drought stress, as a consequence of this global phenomenon, is among the most unfavorable factors that could limit the growth and production of crops worldwide and pose a serious threat to the production of sustainable crops. Since several plant physiological and biochemical relationships under drought conditions remain unknown, it may be possible to obtain more drought-tolerant plants by knowing these details. An effective management strategy involves the use of exogenous substances, increasing the expression of resistant genes, and increasing the production of enzymes that help the plant to withstand damaging environmental conditions such as drought. Experimental treatments consisted of four levels of irrigation regimes and foliar application of abscisic acid (ABA) at two concentrations, with three replicates. The results showed that drought in 30–40% field capacity increased the antioxidant activity by DPPH, ABTS, FRAP, and TAOC methods; and the antioxidant enzymes of catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), and ascorbate peroxidase (APX), significantly. Foliar application of ABA on Lavandula angustifolia cv. Munstead improved plant metabolism under stress conditions, mildly. So that, the interaction between drought and ABA had a synergistic effect on antioxidant activity and related enzymes. The expression of CAT, POD, and APX genes decreased under drought stress, while spraying ABA ameliorated this decrease. The expression of the SOD gene tended to decline, and no drought treatment along with 15 μM ABA spraying revealed the highest expression. Hormone spraying, on the other hand, had a positive effect on this expression under stress compared to the control (no spraying). Overall, despite the unknown details of how radical scavenging functions in plants and the associated expression, these results suggest that ABA treatment reduced the inhibitory effects of drought stress and increased the tolerance of lavender under stress conditions.