physiological and biochemical reactions of hordeum vulgare seedlings to the action of silver nanoparticles

Morphometrical indexes, and spectrophotometrically measured protein and glutathione (GSH, GSSG) contents and activity of peroxidase (POD, EC 1.11.1.7), glutathione-reductase (GR, EC 1.6.4.2) and glutathione S-transferase (GST, EС 2.5.1.18) were examined in Hordeum vulgare L. seedlings after 0.01 and 0.1 mg/l AgNPs treatment during 24 h. We tested the hypothesis that the action of nanoparticles has a stressful effect on the physiological and biochemical processes of seedlings. Growth of roots was inhibited and fresh weight decreased by 29% and 21% under low and high concentrations respectively. Conversely, leaf growth was intensified, and leaf length (16% and 18%) and fresh weight (35% and 44%) increased at low and high concentrations respectively. POD activity in roots increased by 26% and 7%, and decreased in leaves to 57% and 81% of control at low and high concentrations respectively. GSH content changed insignificantly, but GSSG content increased in roots (2 and 2.5-fold) and in leaves (13% and 30%) at both AgNPs concentrations. GSH/GSSG-ratio decreased in roots (1.9 and 2.6-fold) and in leaves (1.1 and 1.3-fold) at low and high concentrations respectively. GR activity decreased at a concentration of 0.01 mg/l (7% in roots and 17% in leaves respectively) and increased at 0.1 mg/l (52% in roots and 6% in leaves). GST activity increased in leaves (52% and 78% at low and high concentrations) but decreased by 17% in roots under high concentration of nanosilver. Thus, the action of AgNPs on barley seedlings had a dose-dependent and organ-specific character. The various directions of changes in growth, metabolic processes and activity of antioxidant defense systems appear to be a stress response of barley seedlings to the impact of AgNPs, which underlines the necessity of detailed study of plant intracellular processes exposed to the action of nanomaterial.