Barium effect on germination, plant growth, and antioxidant enzymes in Cucumis sativus L. plants

Barium (Ba) is a nonessential element that can cause several deleterious effects in most organisms. Elevated Ba concentrations can be toxic for plants and may affect growth and disturbances in homeostasis. This study aimed to evaluate the Ba stress, the plant-tolerance limits, and the detoxification strategy adopted by Cucumis sativus L. The effect of Ba on seed's germination and vegetative development of this species was evaluated. For germination test, different Ba concentrations were used (0, 200, 500, 1,000, and 2,000 μM). Results showed that germination was stimulated with 500 and 2,000 µM of Ba. The toxicity effect on plant development was studied by treating the plants with increasing doses of Ba (100, 200, 300, and 500 μM) during 45 days. Shoot and root dry biomass production decreased significantly with elevated Ba concentrations, although water content enhanced in the roots. The concentration of Ba, 500 µM, induced high Ba accumulation in shoots and roots (9 times higher than in the control plants). Moreover, results showed that catalase, guaiacol peroxidase, and ascorbate peroxidase activities were stimulated in the different tissues of cucumber plants which highlight the occurring of an oxidative damage through Ba treatments and the involvement of the plant enzymatic antioxidant defense system.