Effect of Azolla extract on the salt tolerance of Lentils during germination

Soil salinization is one of the threats that affect the germination, growth, and production of many crops. The present study has evaluated to what degree Azolla piñnata extracts can improve the salt tolerance of lentil (Lens culinaris, Giza 9) seeds. Germination percentage, salt tolerance, plumule, and radicle lengths and seedling vigor index were gradually reduced at 150 and 200 mM NaCl salt stress. While the catalase and ascorbic oxidase enzymes activities were gradually inhibited at the two levels of NaCl salt-stress, peroxidase and polyphenol oxidase activities were significantly enhanced. Total soluble sugar in salt-stressed lentils along with α-amylase activity were also lowered. The level of the phytohormones auxins, gibberellic acids, and zeatin highly decreased at 150 mM NaCl, while the abscisic acid level was not affected. On the other side, H2O2, lipid peroxidation, and proline levels drastically enhanced at 150 and 200 mM NaCl salt stress. Salt-stressed lentil extracts (2, 4, 6, and 8 mg ml^-1) had a high H2O2 scavenging activity percentage compared to unstressed ones. Fresh or boiled extract of Azolla piñnata alleviated all negative effects of 150 mM NaCl salt-stress on lentils by enhancing the activity of the antioxidant enzymes, H2O2 scavenging capacity, α-amylase activity, and elevating soluble sugars, proline, and phytohormones content (particularly gibberellic acid). The fresh extract was more effective than the boiled one to increase the NaCl stress tolerance of lentils. Germination was finally recovered by Azolla extracts which may be considered as a piece of evidence to support the role of the application of Azolla piñnata extracts as a biostimulant to improve germination and early growth of many species under salinity.