Effects of Azospirillum lectin on wheat seedling growth under salt stress

Azospirillum brasilense, which has the potential to stimulate plant growth, belongs to plant-growth-promoting bacteria. The positive effect of Azospirillum on plants may be due to different mechanisms. Azospirilla can assist in mitigation of many kinds of abiotic stress. Lectins are glycoproteins with different molecular masses and carbohydrate specificities. Azospirillum lectins are polyfunctional molecules. They promote plant growth and enzyme activity, they also can alter the plant cell content of stress metabolites, which attests that they can induce adaptation processes in wheat seedling roots. We investigated the dose-dependent effects of the lectin from A. brasilense strain Sp7 on the roots of 4-day-old wheat seedlings (Triticum aestivum L. cv. Saratovskaya 29) grown under salt stress. A low lectin concentration (0.3 mM L-1) improved seedling growth and alleviated the stress-induced growth inhibition. However, higher concentrations of lectin (1.2 mM L-1) did not affect the growth of the stressed seedling roots. In the roots of 4-day-old wheat seedlings under salt stress, the Sp7 lectin decreased total protein content and lipid peroxidation, which causes membrane damage, but increased the content of secondary metabolites such as total phenolics and total flavonoids. We conclude that the Azospirillum lectins are involved in adaptational changes in wheat seedling roots, due to which the relationship between bacteria and their hosts can be regulated under changing soil and climatic factors.