Tredenick E C, Farrell T W, Forster W A
School of Mathematical Sciences, Queensland University of Technology, Brisbane, QLD, Australia.
ARC Centre of Excellence for Mathematical and Statistical Frontiers, Queensland University of Technology, Brisbane, QLD, Australia.
Front Plant Sci. 2018 Dec 20;9:1888. doi: 10.3389/fpls.2018.01888. eCollection 2018.
The agricultural industry requires improved efficacy of sprays being applied to crops and weeds to reduce their environmental impact and increase financial returns. One way to improve efficacy is by enhancing foliar penetration. The plant leaf cuticle is the most significant barrier to agrochemical diffusion within the leaf. The importance of a mechanistic mathematical model has been noted previously in the literature, as each penetration experiment is dictated by its specific parameters, namely plant species, environmental conditions such as relative humidity and spray formulation including adjuvant addition. A mechanistic mathematical model has been previously developed by the authors, focusing on plant cuticle diffusion of calcium chloride through tomato fruit cuticles including pore swelling, ion binding and evaporation, along with the ability to vary the active ingredient concentration and type, relative humidity and plant species. Here we further develop this model to include adjuvant effects as well as the hygroscopic nature of deliquescent ionic solutions with evaporation on the cuticle surface. These modifications to a penetration and evaporation model provide a novel addition to the literature and allow the model to be applied to many types of evaporating ionic hygroscopic solutions on many types of substrates, not just plant cuticles. We validate our theoretical model results against appropriate experimental data, discuss key sensitivities and relate theoretical predictions to physical mechanisms. The important governing mechanisms influencing surfactant enhanced penetration of ionic active through plant cuticles were found to be aqueous pore radius, pore density, cuticle thickness and initial contact angle of the applied droplet; ion binding, relative humidity and evaporation including hygroscopic water absorption parameters for point of deliquescence. The sensitivity analysis indicated surfactants increase penetration by changing the point of deliquescence of a solution, which alters the water absorption and the initial contact angle, which alters the number of pores under the droplet. The results of the validation and sensitivity analysis imply that this model accounts for many of the mechanisms governing penetration in plant cuticles.
农业产业需要提高施用于农作物和杂草的喷雾效果，以减少其对环境的影响并增加经济回报。提高效果的一种方法是增强叶面渗透。植物叶片角质层是农用化学品在叶片内扩散的最重要障碍。文献中先前已指出机理数学模型的重要性，因为每次渗透实验都由其特定参数决定，即植物种类、环境条件（如相对湿度）和喷雾配方（包括助剂添加）。作者先前已开发出一种机理数学模型，重点研究氯化钙通过番茄果实角质层的植物角质层扩散，包括孔隙膨胀、离子结合和蒸发，以及改变活性成分浓度和类型、相对湿度和植物种类的能力。在此，我们进一步开发该模型，以纳入助剂效应以及潮解性离子溶液在角质层表面蒸发时的吸湿特性。对渗透和蒸发模型的这些修改为文献增添了新内容，并使该模型能够应用于多种类型底物上的多种蒸发离子吸湿溶液，而不仅仅是植物角质层。我们根据适当的实验数据验证了理论模型结果，讨论了关键敏感性，并将理论预测与物理机制相关联。发现影响表面活性剂增强离子活性成分通过植物角质层渗透的重要控制机制是水相孔隙半径、孔隙密度、角质层厚度和所施加液滴的初始接触角；离子结合、相对湿度和蒸发，包括潮解点的吸湿吸水参数。敏感性分析表明，表面活性剂通过改变溶液的潮解点来增加渗透，这会改变吸水和初始接触角，进而改变液滴下的孔隙数量。验证和敏感性分析结果表明，该模型考虑了许多控制植物角质层渗透的机制。
