Agrochemical spray formulations applied to plants are often mixed with surfactants that facilitate delivery of the active ingredient. However, surfactants cause phytotoxicity and off-target effects in the environment. We propose the use of nanostructured liquid crystalline particles (NLCP) as an alternative to surfactant-based agrochemical delivery. For this, we have compared the application of commercial surfactants, di (2-ethylhexyl) sulfosuccinate and alkyl dimethyl betaine, with NLCP made from phytantriol, at concentrations of 0.1%, 1% and 5% on the adaxial surface of leaves of four plant species Ttriticum aestivum (wheat), Zea mays (maize), Lupinus angustifolius (lupin), and Arabidopsis thaliana. In comparison with the application of surfactants there was less phytotoxicity on leaves of each species following treatment with NLCP. Following treatment of leaves with NLCP analysis of cuticular wax micromorphology revealed less wax solubilization in the monocot species. The results clearly show that there are advantages in the use of NLCP rather than surfactants for agrochemical delivery.

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Anionic exchange materials, such as layered double hydroxides (or nanoclays) are established delivery vehicles for bioactives in the pharmaceutical industry. In contrast, the use of these same nanoclays for the delivery of agrochemicals is not well explored yet has great potential for transporting and transferring bioactives to plants that compromise agricultural crop productivity. Herein, we have prepared a MgAl-layered double hydroxide (MgAl-LDH) nanoclay loaded with 2,4-dichlorophenoxyacetic acid (2,4-D) and characterized this material using Fourier-transform infrared, nuclear magnetic resonance, X-ray powder diffraction and Transmission electron microscopy. Spray application of agriculturally relevant doses of bare nanoclay (from 0.2% w/v to 1.0% w/v) on to Arabidopsis thaliana plants did not induce cellular damage or stress when tested for the site-specific stress marker, callose (a β-1,3 glucan). In vitro studies showed that the 2,4-D was slowly released from the preloaded nanoclay over 18 h. When compared to positive controls, spray-applied at equivalent doses, the 2,4-D loaded nanoclay applications (from 0.6 to 1.0% w/v) clearly showed a stronger and irreversible herbicidal effect on the test plants. We therefore propose that nanoclay materials have distinct advantages over conventional surfactant-based agrochemical spray applications and can contribute toward advanced agricultural practices.

Electron microscopy techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM) have been invaluable tools for the study of the micromorphology of plant cuticles. However, for electron microscopy, the preparation techniques required may invariably introduce artefacts in cuticle preservation. Further, there are a limited number of methods available for quantifying the image data obtained through electron microscopy. Therefore, in this study, optical microscopy techniques were coupled with staining procedures and, along with SEM were used to qualitatively and quantitatively assess the ultrastructure of plant leaf cuticles. Leaf cryosections of Triticum aestivum (wheat), Zea mays (maize), and Lupinus angustifolius (lupin) were stained with either fat-soluble azo stain Sudan IV or fluorescent, diarylmethane Auramine O and were observed under confocal laser scanning microscope (CLSM). For all the plant species tested, the cuticle on the leaf surfaces could be clearly resolved in many cases into cuticular proper (CP), external cuticular layer (ECL), and internal cuticular layer (ICL). Novel image data analysis procedures for quantifying the epicuticular wax micromorphology were developed, and epicuticular waxes of L. angustifolius were described here for the first time. Together, application of a multifaceted approach involving the use of a range of techniques to study the plant cuticle has led to a better understanding of cuticular structure and provides new insights into leaf surface architecture.

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