Next Generation Optical Analysis for Agrochemical Research & Development

The world’s population is increasing rapidly and higher calorific diets are becoming more common; as a consequence the demand for grain is predicted to increase by more than 50% by 2050 without a significant increase in the available agricultural land. Maximising the productivity of the existing agricultural land is key to maintaining food security and agrochemicals continue to be a key enabler for the efficiency gains required. However, agrochemicals can be susceptible to significant losses and thus often require further chemical to be applied to compensate. Sources of such losses include spray drift, poor spray retention/capture by the target and poor penetration through the plant cuticle. The effectiveness of a crop protection agent depends not only on the intrinsic activity of the active ingredient (AI) but also on the physicochemical properties of the formulation. These properties can be modified by using formulation components, known as adjuvants, which can be used to help mitigate such losses. Adjuvants exert their effects by, for example, controlling droplet size and distribution through their effect on surface tension which can also improve penetration into leaves through the cuticle wax which coats the epidermis of leaves and acts as a protective barrier. However, characterising how they alter the movement of the AIs can be challenging. Optical techniques have shown promise in a multitude of scientifically related areas, such as in vivo tissue imaging, but none have yet been applied to aiding the agrochemical industry. By probing the interactions between leaf surface and agrochemical agent, with light, one is able to obtain a large amount of diagnostic information, non-invasively. Whereas techniques like Raman 3 spectroscopy are limited by long acquisition times, coherent Raman techniques such as coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) are coherently driven and provide an enhanced signal, and also allow for video-rate imaging. In this thesis, I have applied this cutting-edge laser imaging technique as a novel analytical technique that allows the in situ analysis of agrochemicals in living plant tissues at a cellular level. In Chapters 4 through 7, multiple factors essential for a functional and efficient agrochemical were considered and experimented. In Chapter 4, a typical industry study highlights the need for innovative and rapid technologies in the agrochemical industry. The resulting chapters (5, 6, and 7) outline several ways in which Coherent Raman Scattering (CRS) techniques can improve the current capabilities of agrochemical testing. By utilising a model system, paraffin wax, a cheap and rapid protocol can provide accurate diffusion information and repeatable results. Chapters 6 and 7 use both this protocol to gain comparative data on several adjuvants and active ingredients in paraffin wax and in vivo, in a variety of plants. The ability to visualise agrochemical products on a leaf surface to reveal interactions between the materials of the product and with the leaf surface will enable a step change in the agrochemical design process, through determination of the spatial distribution of the materials and their roles within the applied products. It is hoped that the technology developed in this thesis could play a big role in the development of future agrochemical products that are tailored to maximise efficacy and minimise environmental impact