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 activity was gradually inhibited at the two levels of NaCl salt-stress, peroxidase and polyphenol oxidase activity was significantly enhanced. Total soluble sugar in salt-stressed Lentils along with α-amylase activity was also lowered. The phytohormones auxins, gibberellic acids, and zeatin were highly decreased at 150 mM NaCl, while the abscisic acid level was not affected. On the other side, H2O2, lipid peroxidation, and proline levels were drastically enhanced at 150 and 200 mM NaCl salt stress. Salt-stressed Lentilsʹ 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). Germination was finally recovered by Azolla extracts which may be considered as a piece of evidence to support the application of Azolla piñnata extracts as a biostimulant to improve germination and early growth of many species under salinity.