Pesticides may indeed kill plant pathogens, but they're also harmful to the environment. Newly developed nanoparticles may provide a more eco-friendly alternative, as they boost the immune systems of crop plants, then harmlessly dissolve.
Occurring naturally in soil, a compound known as silicic acid has for some time been known to provoke plants' immune response. It's also released by amorphous (non-crystalline) silica nanoparticles, which are found in some crop plants. Such nanoparticles are additionally an ingredient in food-grade silica, which is used as an anti-clumping agent in products like table salt and protein powders.
Silicic acid is already applied to crops in liquid fertilizer form, to help them fight off viruses and problematic bacteria. Unfortunately, though, the sudden and intense dose of the compound can actually stress the plants, plus it may harm beneficial microorganisms living in the soil.
Seeking a gentler approach, scientists at Switzerland's University of Fribourg have created synthetic silica nanoparticles which are rich in silicic acid, but that release it slowly. In lab tests, these were applied to thale cress plants (Arabidopsis thaliana) that were infected with Pseudomonas syringae bacteria.
It was found that the acid helped the plants to fight off the microbes, by increasing production of a key defense hormone. Importantly, though, the nanoparticles entered the plants solely through the respiratory stomata pores on their leaves. The particles proceeded to perform all of their immune-boosting functions within the leaves, not travelling into the stems or roots – thus minimizing stress to the plants.
Additionally, the nanoparticles reportedly degraded without leaving a trace, in the presence of water. This means that they shouldn't build up in the soil, or be passed through to people consuming the crops.
The scientists are now investigating the effectiveness of the nanoparticles on other bacteria and viruses, along with the long-term effects of the technology upon the environment.
A paper on the research, which is being led by Dr. Fabienne Schwab and Dr. Mohamed El-Shetehy, was recently published in the journal Nature Nanotechnology.
Source: Adolphe Merkle Institute at the University of Fribourg