Silicon application can improve productivity outcomes for salt stressed plants. Here, we describe how strawberry plants respond to treatments including various combinations of salt stress and nano-silicon dioxide, and assess whether nano-silicon dioxide improves strawberry plant tolerance to salt stress. Strawberry plants were treated with salt (0, 25 or 50 mM NaCl), and the nano-silicon dioxide treatments were applied to the strawberry plants before (0, 50 and 100 mg L⁻¹) or after (0 and 50 mg L⁻¹) flowering. The salt stress treatments reduced plant biomass, chlorophyll content, and leaf relative water content (RWC) as expected. Relative to control (no NaCl) plants the salt treated plants had 10% lower membrane stability index (MSI), 81% greater proline content, and 54% greater cuticular transpiration; as well as increased canopy temperature and changes in the structure of the epicuticular wax layer. The plants treated with nano-silicon dioxide were better able to maintain epicuticular wax structure, chlorophyll content, and carotenoid content and accumulated less proline relative to plants treated only with salt and no nano-silicon dioxide. Analysis of scanning electron microscopic (SEM) images revealed that the salt treatments resulted in changes in epicuticular wax type and thickness, and that the application of nano-silicon dioxide suppressed the adverse effects of salinity on the epicuticular wax layer. Nano-silicon dioxide treated salt stressed plants had increased irregular (smoother) crystal wax deposits in their epicuticular layer. Together these observations indicate that application of nano-silicon dioxide can limit the adverse anatomical and biochemical changes related to salt stress impacts on strawberry plants and that this is, in part, associated with epicuticular wax deposition.

One-year-old olive (Olea europaea L. cv. Zard) plants were treated with 0.5, 1, and 2 mM salicylic acid (SA) and then exposed to nonfreezing and freezing temperatures (−5, −10, and −20°C) for 10 h. Untreated plants served as a control. Exposure to freezing temperatures caused a considerable increase in ion leakage and lipid peroxidation in olive leaves. Treatment with suitable exogenous SA (1.0 mM) prevented the increase in the ion leakage and lipid peroxidation caused by freezing temperatures, especially at −5 and −10°C. SA-induced freezing tolerance was accompanied by increased activities of antioxidant enzymes, such as guaiacol peroxidase, catalase, ascorbate peroxidase, and polyphenol oxidase, as compared to control plants. Proline, total phenolic content, and antioxidant capacity of olive leaves were declined significantly after exposure to freezing temperature, and their content decreased with lowering of freezing temperatures, while treatment with 1 mM SA induced a significant increase in their content. As a summary of these results, suitable concentration of SA (1 mM) could enhance freezing tolerance of olive plant by increasing antioxidant enzyme activities and decreasing MDA content through cell membrane integrity maintenance.