Silicon enhances the growth of nickel-stressed cabbage plants by reducing oxidative damage and strengthening root architecture

Nickel (Ni) toxicity can disorder plant growth and development, while silicon (Si) is important element in ameliorating heavy metal stress. This study investigated the effect of exogenous application of Si (2 mM) on cabbage plants exposed to Ni (0.5 mM and 1 mM). The impacts of exogenous Si application on root morphology, enzymatic activities, proline and glycine betaine (GB) accumulation, reactive oxygen species (ROS), and other physiological parameters of cabbage plants grown under Ni stress were observed. Exogenous Si mitigated the irreversible damage caused by Ni by improving root morphology, enhancing plant enzymatic activities, regulating osmoprotectants (proline and glycine betaine), modulating ROC (<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msubsup><mml:mrow><mml:mi>O</mml:mi></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow><mml:mrow><mml:mo>-</mml:mo></mml:mrow></mml:msubsup></mml:mrow></mml:math> and H₂O₂), and supporting overall plant physiology. Furthermore, Si reduced Ni content by 67% and 72% in roots and leaves, respectively, and improved the nutrients (Si, N, P, and K) upregulation under Ni stress while reducing oxidative stress. The overall findings suggest that foliar application of 2 mM Si can enhance root morphology, regulate nutrient uptake, and play a crucial role in reducing Ni accumulation. This effect is primarily attributed to its contribution to strengthening plant defense mechanisms against oxidative damage and regulating osmoregulation, thereby alleviating Ni-induced stress and promoting plant growth.