The Effect of Putrescine and 24-Epibrasinolide on the Activity of Antioxidant Enzymes in Basil to under Drought Stress

This paper aims at evaluating the effects of putrescine and 24-epibrasinolide on altering the activity of antioxidant enzymes to tolerate drought stress in basil. The plan has been implemented as factorial split plot layout based on a randomized complete block design with three replications in the cropping years 2017-2018 and 2018-2019 at the research farm of the Faculty of Agriculture, Ilam University. Experimental treatments include drought stress at three levels (40, 80, and 120 mm evaporation from Class A evaporation pan) as the main plots, putrescine foliar application at three levels (0, 0.5, and 2 (mM) and 24- Epibrassinolid foliar application at three levels (0, 0.5, and 2 μM) as subplots. Results show that the highest amount of proline in 120 mm occurs during the first year of the experiment and the use of putricin (2 mM) and 24-epibrasinolide (0.5 μM) also cause a further increase in proline. The highest amount of catalase has been observed in the 120 mm evaporation treatment and the application of 2 mM putrescine. The interaction of drought stress, putrescine, and 24-epiprasinolide also show that the highest levels of ascorbate peroxidase and superoxide dismutase belong to the treatment of 120 mM where the highest concentrations of putrescine (2 mM) and 24-epibrasinolide (2 μM) is observed. Under optimal irrigation conditions (40 mm), the combined application of lower concentrations of putrescine (0.5 mM) and epibrasinolide (0.5 μM) and under drought stress conditions (80 and 120 mm), higher concentrations of these two substances (2 mM putrescine and 2 μM epibrasinolide) increase the enzyme guaiacol peroxidase. Multiple interactions of year, drought stress, putrescine, and 24-epibrasinolide have had a significant effect on total flavonoids and essential oil percentage of basil. In both experimental years, application of 2 mM putrescine and 2 μM 24-epibrasinolide at all levels of drought stress 120 mm cause a further increase in these two traits which has been greater in the first year than the second one. Concomitant use of 2 mM putrescine and 2 μM epibracinolide due to increased proline synthesis and antioxidant enzymes is the best treatment to reduce the effects of drought stress in basil, indicating a synergistic relation between the two. The substance boosts the growth of basil, increasing the percentage of its essence.