Halophilic microalgae Dunaliella salina extracts improve seed germination and seedling growth of Triticum aestivum L. under salt stress

Salinity is among the major limiting factors of crop productivity worldwide. Salt stress affects the plant growth at all developmental stages. The present study investigates the potential of halotolerant microalgae Dunaliella salina extracts to suppress the inhibition of seeds germination and seedlings growth caused by salt stress on wheat (Triticum aestivum). Germination percentage and height of coleoptiles and root system were measured as a response of D. salina extracts treatment. Biomass hydrolyzate of D. salina cultured in different concentrations of NaCl (1, 2 and 4 M of NaCl) improved germination and seedling growth of wheat under salt stress. The effect of molecules accumulated in D. salina which are proline, carotenoids and exopolysaccharides on germination and seedling growth was investigated. Our results showed that exopolysaccharides extracted from the microalgae had the major stimulating effect on germination and seedling growth in wheat. Exopolysaccharides extracts from D. salina improved the germination percentage of wheat seeds under salt stress of 3 and 6 g L-1 NaCl by 96 and 83%, respectively, compared to control, while the height of root system was stimulated with 133 and 444% and the coleoptiles height was increased by 105 and 750% in response to 3 and 6 g L-1 NaCl, respectively, compared to control stressed untreated. Our study demonstrates that extracts of halotolerant microalgae especially exopolysaccharides could help plants to tolerate salt stress.