Improving Impact of Poly(Starch/Acrylic Acid) Superabsorbent Hydrogel on Growth and Biochemical Traits of Sunflower Under Drought Stress

A superabsorbent hydrogel (SAH) composite from starch and polyacrylic acid p(St/AAc) was prepared by free radical polymerization in the presence of potassium persulfate initiator. The effects of two polymer composition on gel fraction, swelling, and water retention have been investigated. It was found that swelling was extremely sensitive to the acrylic acid contents; it increased with the decrease of acrylic acid content. Moreover, the hydrogel samples showed an excellent water retention capability. The swelling kinetics and water diffusion mechanism in distilled water were also discussed in order to choose appropriate SAH functioning as soil conditioner of sunflower under drought stress. A pot experiment was carried out to study the ameliorative role of SAH application on sunflower (Helianthus annuus L. Var Sakha) plants grown under drought stress. Growth parameters, content of photosynthetic pigments, total proline and phenol, and antioxidant enzymes were determined. The shoot and root length increased up to 49.84% and 5.35% rather than in the absence of SAH. Growth parameters and photosynthetic pigments of sunflower plants grown under drought in the absence of SAH were reduced. Hydrogel application enriched the photosynthetic pigment. Besides, it also decreased the harmful impacts of drought on sunflower plants. The results herein demonstrated that the hydrogel decreased the proline, total phenols, catalase, peroxidase, and polyphenol oxidase content. The findings of this study indicate that the use of hydrogel can be considered as an unconventional and novel tool in the mitigation of drought stress.