Layered double hydroxide (LDH) nanoparticles enable foliar delivery of genetic material, herbicides, and nutrients to promote plant growth and yield. Understanding the foliar uptake route of nanoparticles is needed to maximize their effectiveness and avoid unwanted negative effects. In this study, we investigated how delivering layered double hydroxide (d = 37 ± 1.5 nm) through the adaxial (upper) or abaxial (lower) side of leaves affects particle uptake, nutrient delivery, and photosynthesis in tomato plants. LDH applied on the adaxial side was embedded in the cuticle and accumulated at the anticlinal pegs between epidermal cells. On the abaxial side, LDH particles penetrated the cuticle less, but the presence of the stomata enables penetration to deeper leaf layers. Accordingly, the average penetration levels of LDH relative to the cuticle were 2.47 ± 0.07, 1.25 ± 0.13, and 0.75 ± 0.1 μm for adaxial, abaxial with stomata, and abaxial without stomata leaf segments, respectively. In addition, the colocalization of LDH with the cuticle was ∼2.3 times lower for the adaxial application, indicating the ability to penetrate the cuticle. Despite the low adaxial stomata density, LDH-mediated delivery of magnesium (Mg) from leaves to roots was 46% higher for the adaxial than abaxial application. In addition, adaxial application leads to ∼24% higher leaf CO₂ assimilation rate and higher biomass accumulation. The lower efficiency from the abaxial side was, at least partially, a result of interference with the stomata functionality which reduced stomatal conductance and evapotranspiration by 28% and 25%, respectively, limiting plant photosynthesis. This study elucidates how foliar delivery pathways through different sides of the leaves affect their ability to deliver active agents into plants and consequently affect the plants' physiological response. That knowledge enables a more efficient use of nanocarriers for agricultural applications.

中文翻译：

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纳米载体叶面吸收途径影响活性剂的递送和植物的生理反应


层状双氢氧化物 （LDH） 纳米颗粒能够叶面递送遗传物质、除草剂和养分，以促进植物生长和产量。需要了解纳米颗粒的叶面吸收途径，以最大限度地提高其有效性并避免不必要的负面影响。在这项研究中，我们研究了通过叶片的近轴（上）或远轴（下）侧输送层状双氢氧化物 （d = 37 ± 1.5 nm） 如何影响番茄植株的颗粒吸收、养分输送和光合作用。应用于近轴侧的 LDH 嵌入角质层并积聚在表皮细胞之间的背斜钉处。在远轴侧，LDH 颗粒对角质层的渗透较少，但气孔的存在能够渗透到更深的叶层。因此，LDH 相对于角质层的平均渗透水平分别为 2.47 ± 0.07、1.25 ± 0.13 和 0.75 ± 0.1 μm，用于近轴、远轴有气孔和远轴无气孔叶段。此外，对于近轴应用，LDH 与角质层的共定位降低了 ∼2.3 倍，表明能够穿透角质层。尽管近轴气孔密度低，但 LDH 介导的镁 （Mg） 从叶到根的递送在近轴应用中比远轴施用高 46%。此外，近轴施用导致叶片 CO₂ 同化率提高约 24% 和生物量积累增加。远轴侧的较低效率至少部分是由于对气孔功能的干扰，这分别降低了气孔导度和蒸散 28% 和 25%，限制了植物的光合作用。 本研究阐明了通过叶子不同侧面的叶面递送途径如何影响它们将活性剂递送到植物中的能力，从而影响植物的生理反应。这些知识使纳米载体能够更有效地用于农业应用。