Delivery, Fate, and Mobility of Silver Nanoparticles in Citrus Trees

Abstract

Crop disease control is crucial for the sustainable development of agriculture, with recent advances in nanotechnology offering a promising solution to this pressing problem. However, the efficacy of nanoparticle (NP) delivery methods has not been fully explored, and knowledge regarding the fate and mobility of NPs within trees is still largely unknown. In this study, we evaluate the efficiency of NP delivery methods and investigate the mobility and distribution of NPs with different surface coatings (citrate (Ct), polyvinylpyrrolidone (PVP), and gum Arabic (GA)) within Mexican lime citrus trees. In contrast to the limited delivery efficiency reported for foliar and root delivery methods, petiole feeding and trunk injection are able to deliver a large amount of NPs into trees, although petiole feeding takes much longer time than trunk injection (7 days vs 2 h in citrus trees). Once NPs enter plants, steric repulsive interactions between NPs and conducting tube surfaces are predicted to facilitate NP transport throughout the plant. Compared to PVP and Ct, GA is highly effective in inhibiting the aggregation of NPs in synthetic sap and enhancing the mobility of NPs in trees. Over a 7 day experimental period, the majority of the Ag recovered from trees (10 mL, 10 ppm GA-AgNP suspension) remain throughout the trunk (81.0% on average), with a considerable amount in the roots (11.7% on average), some in branches (4.4% on average), and a limited amount in leaves (2.9% on average). Furthermore, NP concentrations during injection and tree incubation time postinjection are found to impact the distribution of Ag in tree. We also present evidence for a transport pathway that allows NPs to move from the xylem to the phloem, which disperses the NPs throughout the plant architecture, including to the roots.

Trunk Injection as a Tool to Deliver Plant Protection Materials—An Overview of Basic Principles and Practical Considerations

“…'Tree Tech ® OTC' is an oxytetracycline calcium complex registered for use in crop-bearing peaches and pears for bacterial blast, blossom blight, and fire blight management, and X-disease of peaches; however, there are few other bactericides registered for injection in crop-bearing trees. Oxytetracycline Effective [136,161] Most recently, injection experiments have extended beyond fungicides, insecticides, and bactericides to include other compounds such as plant defense activators [114,161,174], RNA [28,175], plant growth regulators [176], nanoparticles [177][178][179], novel antimicrobial molecules [180], essential oils [181], biofertilizers [182], nutrients [183], nano-carrier treatments [97], and bacteria [157,[184][185][186]. However, none are currently used on a commercial basis.…”

Nanoparticle-Based Sustainable Agriculture and Food Science: Recent Advances and Future Outlook

“…It shows that the uptake of NMs is highly dependent on the type of delivery method used. In this context, Su et al investigated the fate and mobility of surface-modified AgNP delivery to trees by employing various methods, including direct tree injection and petiole feeding in Mexican lime citrus trees (Su et al, 2020). Further explanation of uptake and transport in conjunction with the fate and transformation of NMs is comprehensively reviewed by different groups (Lv et al, 2019;Su et al, 2019).…”

Phytonanotechnology applications in modern agriculture

“…Moreover, the NPs surface charge can be improved by coating, which contributes to their translocation [ 37 ]. Recent reports found that the material of surface coating can prevent the closure of stomata by decreasing the indiscriminate gathering of NPs, thus enhancing the absorption of NPs in crops [ 38 ]. Moreover, the utilization of functional groups and surfactants improves the bioavailability of NPs by increasing the NPs adhesion on the surface of leaves [ 39 , 40 ].…”