Nanostructured mesoporous silica materials induce hormesis on chili pepper (Capsicum annuum L.) under greenhouse conditions

Current agricultural practices for vegetable production are unsustainable, and the use of certain nanomaterials has shown significant potential for either plant growth promotion or defense induction in crop species. The aim of the present work was to evaluate the possible effects of two SBA nano-structured silica materials differing in morphology; SBA-15, with porous structure in parallel and with a highly ordered hexagonal array and SBA-16, with spheric nano-cages located in cubic arrays, as plant growth promoters/eustressors on chili pepper (Capsicum annuum L.) during cultivation under greenhouse conditions. The study was carried out at three foliarly applied concentrations (20, 50 and 100 ppm) of either SBA materials to determine effects on seed germination, seedling growth, plant performance and cold tolerance under greenhouse. Phytotoxicity tests were carried out using higher concentrations (100, 1000 and 200 ppm) applied by dipping or spraying onto chili pepper plants. Deionized water controls were included. The results showed that the SBA materials did not affect seed germination; however, SBA-15 at 50 ppm and 100 ppm applied by imbibition significantly increased seedling height (up to 8-fold) and provided enhanced growth performance in comparison with controls under select treatment regimes. Weekly application of SBA-15 at 20 ppm significantly increased stem diameter and cold tolerance; however, SBA-16 showed significant decreases in plant height (20 ppm biweekly applied) and stem diameter (20, 50 and 100 ppm biweekly applied). The results demonstrate that both SBA materials provided hormetic effects in a dose dependent manner on chili pepper production and protection to cold stress. No phytotoxic response was evident. These findings suggested the nanostructured mesoporous silica have potential as a sustainable amendment strategy to increase crop production under stress-inducing cultivation conditions.