Change in activity of antioxidative enzymes in young leaves of sunflower (Helianthus annuus L.) by application of super absorbent synthetic polymers under drought stress condition

Drought stress causes molecular damage to plants, either directly or indirectly through formation of reactive oxygen species (ROS). Alteration of antioxidant enzymes activities is an element in the defense process. Changes in antioxidant enzymes activities and seed yield in sunflower (Helianthus annuus L. cv. master) were investigated under drought stress and super absorbent synthetic polymer application. The experiment was carried out in a split plot based on randomized complete block design with three replications. Three irrigation levels after 6 (I-1), 10 (I-2) and 14 (I-3) days and five amounts of super absorbent polymer (0, 75, 150, 225, 300 kg/ha) were set as main and sub factors, respectively. Drought stress was applied at fourteen-leave-stage of sunflower and polymer was added at the same stage to soil in depth of root development. Our results showed that by increasing irrigation intervals, seed yield was decreased significantly. On the other hand, polymer application reduced the harmful effects of drought stress whereas application of 300 kg/ha polymer in long irrigation intervals a reasonable seed yield obtained. According to the results, drought stress induced increases in catalase (CAT), ascorbate peroxidase (APX) and guaiacol peroxidase (GPX) activities. The antioxidant enzymes activities in drought-stressed plants might be accompanied with the production of active oxygen species (AOS). Application of a lower dose of polymer (75 Kg/ha) moderated the negative effects of drought stress, while higher doses of the polymer (225 and 300 kg/ha) prohibited the bad effects of drought stress. In total, our results suggest that application of polymers could be advantageous against drought stress, and could protect sunflower plants in drought stress conditions.