doi:10.1038/nindia.2015.145 Published online 29 October 2015
Researchers have discovered that treating tea leaves with chitosan nanoparticles increases the levels of defense-related enzymes and activate genes, which protect plants against various diseases1. These nanoparticles are thus promising for fighting diseases that cause crop losses.
Synthetic chemicals used to fight plant diseases are harmful to humans. Alternative strategies involve using metal nanoparticles, but they are unstable and toxic. Chitosan, a natural biopolymer, has been shown to protect plants against diseases.
To probe the protective role of chitosan nanoparticles, the researchers treated fresh tea leaves with solutions of chitosan nanoparticles and compared them with chitosan-treated and untreated leaves at room temperature.
After 24 hours, the levels of defense enzymes in the nanoparticle-treated tea leaves increased significantly. These increases were much higher than those of chitosan-treated leaves. Treating the leaves with the nanoparticles also enhanced the levels of superoxide dismutase and catalase ― two antioxidant enzymes that inhibit the increased production of cell-damaging reactive oxygen species in diseases.
The nanoparticle treatment boosted the levels of phenols, which are a part of the natural defense system of plants. Nitric oxide, a signaling molecule, also increased following the nanoparticle treatment. Inhibiting nitric oxide synthesis significantly disrupted the immune responses induced by the nanoparticles, suggesting that this molecule may play a role in the immune responses of plants.
Since chitosan nanoparticles are non-toxic and biodegradable, they could be used for sustainable organic cultivation, the researchers say.