Agricultural scientists at the University of Manchester, England, are making groundbreaking discoveries on the way that the protective wax on leaves operates. By doing so they hope to increase their understanding of the dynamics of pesticides so that future agrichemical products are more efficient.
In research that was supported by the agrochemical company Syngenta, the researchers even constructed a model of a leaf with a replica wax coating, and by using neutron reflectometry have been able to learn about its thickness, chemical properties and how liquids penetrate this layer.
The online journal ScienceDaily explains how this was achieved, writing, “To make the model of the leaf surface, scientists first extracted real plant wax from barley and wheat leaves. This was made possible by a new technique called supercritical carbon dioxide extraction, where scientists dissolve the wax off the surface of the leaf using a carbon dioxide solvent under its supercritical condition at a very high temperature and pressure. When the pressure and temperature is reduced, the carbon dioxide evaporates, leaving behind the wax. This technique was developed in the Green Chemistry Department at the University of York.
The team from the University of Manchester then took the extracted wax and spin coated it onto a flat a silicon support in order to model the leaf surface. Imaging techniques allowed the team to see that the wax model was very similar to the structure of the wax on a real leaf, meaning the model could be used to realistically study how pesticides cross the wax barrier to get into the plant.
In a technique known as neutron reflectometry, the team used ISIS instrument, INTER to bounce neutrons off the surface of the wax model. They found that the wax was made up of a thin underlying film covered by large crystalline structures.”
When discussing the research with the open source scientific website AlphaGalileo, lead author of the study, Elias Pambou from the University of Manchester said, “Neutron reflectometry is so effective because not only can we look at the thickness of the wax films but also the change in density over the thickness range. We’re able to look at the amount of water penetrating into the leaf at the surface of the wax compared to the bottom of the wax closest to the epicuticular plant cells. That could give us a lot of information regarding how the water is diffusing through the plant.”
The research is significant given the current trend of problems that the crop protection industry is fighting. As Julian Gold, Farm Manager of the Hendred Estate in Oxfordshire outlines, “We are currently facing multiple challenges on the pesticide front as there are increasing levels of resistance developing in weeds, pests and diseases as well as a reducing pesticide armoury due to tighter conditions being imposed for registration of products.” He continued by outlining the importance of further pesticide research, saying, “Any research that can improve the efficacy of products through a better understanding of the way that diseases and pesticides penetrate the waxy layer on leaf surfaces should be incredibly useful.”
In a field of research where the study of the nanoworld is playing an ever-larger role, analysis of the crucial interaction between liquids at the leaf’s surface and the way that chemicals are and are not able to interpenetrate plant cells is part of the next wave of crop protection products. As Elias Pambou explains, “By understanding how surfactants in pesticides interact with the plant you can fine-tune the ingredients of the pesticide to not only further increase crop yield but take away some potential negative side effects, including the removal of some of the waxes which leaves the plant susceptible to other sorts of diseases and attack from bacteria and microbes. This opens the door to crop-safe formulations which will reversibly interact with the plant waxes.”
How long it will take for the improved understanding of leaf wax dynamics to produce improved crop protection products is not known, but without a full understanding of the way in which plants protect themselves previous agri-product development has always been working with an unknown x-factor.
Now that researchers have a clearer picture of a plant’s natural defences and the way that chemicals and liquids penetrate those defences, it is hoped that cheaper and more efficient agricultural products may soon be on the market.