Effect of Azospirillum brasilense lipopolysaccharides on the cucumber plant growth. The effect of Azospirillum brasilense Sp245 lipopolysaccharides (LPS) on plant growth, total phenols content, and in situ peroxidase (POD) anzyme activity on cucumber plants (Cucumis sativus) was analyzed in this work. Five days after germination, LPS (10 y 100 µg/ml) were sprayed in the foliage every week during 2 months. Parameters were evaluated in plants of 3 months old. Both concentrations of LPS increased total length of the plants related to untreated controls, however only the concentration of 10 µg/ml notably increased total fresh weight. Total phenols content was highly increased in leaf with both LPS concentrations. Only the LPS concentration of 100 µg/ml stimulated the in situ POD activity. The results suggest that the LPS have the hability to stimulate responses associated with growth and defense in cucumber plants.