Improved growth indices and tolerance of myrtle (Myrtus communis L.) to water-deficit stress by alleviating antioxidants and compatible osmolytes using a superabsorbent polymer

Superabsorbent polymers (SAPs) are able to increase soil moisture and improve plant growth. A greenhouse experiment was conducted to investigate the interaction between different irrigation levels (100% field capacity (FC), 75% FC, and 50% FC) and A200-SAP (0, 1, and 2 g kg-1 dry soil weight) in 1-year old myrtle plants. The results showed that water-deficit treatment (50% FC) significantly reduced growth indices and also increased proline, total phenol, and the activities of antioxidant enzymes compared to well-watered plants (100% FC). While, total soluble protein, flavonoids, and total antioxidant capacity (TAC) had no significant change by increasing water-deficit stress compared to control, added SAP (2 gr kg -1) led to an increase of about 43.81% in root length compared to non- SAP treatment at 50% FC. Furthermore, the use of SAP (2 gr kg -1) significantly increased the content of proline and the activities of antioxidant enzymes, especially catalase (CAT), under water-deficient conditions by providing more water and reducing reactive oxygen species. The results indicated that young myrtle plants are highly adapted to adverse environmental conditions by increasing antioxidant compounds and osmoregulators. Moreover, they could produce new shoot primordia when SAP is added, in both well-water and water-deficient treatments. Therefore, SAPs can be applied in a cost-efficient and efficient manner to the roots of young woody plants to increase their survival and performance efficiency.