必需营养素最常用于土壤和植物叶片，土壤施肥更受欢迎，对更大的养分需求更有效Essential nutrients are most commonly applied to soil and plant leaves, and soil fertilization is more desirable and effective for larger nutrient needs[19]。然而，在某些情况下，叶面施肥因其更具成本效益和效率的特点而成为一种广泛而常见的作物管理方法In some cases, however, foliar fertilization has become a widespread and common method of crop management due to its more cost-effective and efficient characteristics[19]。.

植物的叶子可以保护植物免受水分流失、害虫和病原体的侵害，同时允许气体交换以进行光合作用反应The leaves of the plant protect the plant from water loss, pests and pathogens, while allowing gas exchange for the photosynthetic reaction[20]。叶子的表面通常由特征组成：毛状体、气孔和韧皮部孔。.The surface of a leaf is usually composed of features: trichosomes, stomata, and phloem pores. NPs以两种方式被叶子吸收，即角质层途径和气孔途径 is absorbed by leaves in two ways, namely the cuticle pathway and the stomatal pathway[21]（图2）。直径小于NPs with a diameter of less than 4.8 nm的NPs可以通过角质层通道直接进入叶片[22]，而粒径较大的NP can enter the leaf directly through the cuticle channel, while NPs with a larger diameter can enter through the stomata. Due to the high density of the stomata itself, the stomatal pathway is considered to be a more efficient way to abs可以通过气孔进入。由于气孔本身密度高，气孔通路被认为是吸收orb NP的更有效途径[23]。.NF被气孔吸收后，通过韧皮部转移到植物的其余部分。纳米颗粒可以通过两种方式进入韧皮部，直接从韧皮部细胞进入韧皮部，或者通过韧皮部细胞的间隙进入韧皮部 is absorbed by the stomata and transferred to the rest of the plant through the phloem. Nanoparticles can enter phloem in two ways, either directly from phloem cells or through the interstitiums of phloem cells [24]。纳米肥料可以促进植物生长部位快速获取养分，从而增加叶绿素的产生、光合速率，并最终增加植物的生长发育. Nano-fertilizer can promote the rapid acquisition of nutrients in plant growth parts, thereby increasing chlorophyll production, photosynthetic rate, and ultimately increase plant growth and development[25]。.

纳米肥料由于其独特的特性，在提高养分利用效率方面变得越来越重要Nano-fertilizers are becoming more and more important in improving nutrient utilization efficiency due to their unique properties[28]。纳米肥料有助于以缓慢、可控的方式释放养分，以便将养分输送到目标位置，从而将损失降至最低Rice fertilizer helps to release nutrients in a slow, controlled manner in order to deliver nutrients to the target location, thereby minimizing losses[29]。纳米肥料由于尺寸小，比传统肥料具有更大的吸收和保留能力Nano-fertilizers have greater absorption and retention capacity than traditional fertilizers due to their small size [30]。纳米肥可以改善植物的生理生化指标，如光合速率和养分吸收效率等，增强植物的防御系统. Nano-fertilizer can improve the physiological and biochemical indexes of plants, such as photosynthetic rate and nutrient absorption efficiency, and enhance the defense system of plants[7]。一些研究报道，锌Some studies have reported that zinc NFs具有更好的理化性质，在促进种子发芽和植物生长方面起着积极作用 has better physical and chemical properties and plays a positive role in promoting seed germination and plant growth [31\u201232]。. Ahmed等人表明，硫纳米肥料不仅可以减轻砷的毒性，还可以提高水稻的产量和质量 et al. have shown that sulfur nanofertilizers can not only reduce arsenic toxicity, but also improve the yield and quality of rice[33]。Hu 等人证明，低水平的et al. proved that low levels of TiO2NPs在不引起显著氧化应激的情况下改善了植物营养品质[ improved plant nutritional quality without causing significant oxidative stress [34]。总体而言，纳米肥料比传统肥料更有效，具有良好的发展前景。]. In general, nano-fertilizer is more effective than traditional fertilizer and has good prospects for development.

叶面施肥比土壤施肥更有效，是满足高等树种需求的有用方法Foliar fertilization is more effective than soil fertilization and is a useful method to meet the needs of higher tree species (Figure 3). Compared with foliar application, soil application is more harmful to the environment, and nano-fertilizer has lower bioavailability in the soil, while foliar application has lower environmental risk, so plants generally prefer foliar application of nano-fertilizer. Foliate fertilization has a low exposure dose, can be applied repeatedly, and can be applied regularly according to the weather to avoid nutrient loss. In addition, foliar application provides faster nutrient uptake than soil application[35]（图3）。与叶面施用相比，土壤施用对环境的危害更大，纳米肥料在土壤中的生物利用度较低，而叶面施用的环境风险较低，因此植物通常更喜欢叶面施用纳米肥料[36]。叶面施肥的暴露剂量低，可反复施用，并可根据天气定时施用，避免养分流失[11]。此外，叶面施用比土壤施用提供更快的养分吸收[37]。图3说明了叶面施肥的优点及其对植物的积极影响。.Figure 3 illustrates the advantages of foliar fertilization and its positive effects on plants.

锌（Zinc (Zn）作为一种必需的微量营养素，对植物有重大影响，包括蛋白质、DNA和RNA的合成，也是许多抗氧化酶所必需的辅助因子。关于叶面喷施锌基纳米肥对作物的有利影响的研究很多。), as an essential micronutrient, has a major impact on plants, including protein, DNA, and RNA synthesis, and is also an essential cofactor for many antioxidant enzymes. There are many studies on the beneficial effects of zinc-based nano-fertilizer spraying on crops. Lorenzo等人发现，由于 et al found that ZnO NPs穿透叶片的能力提高， improved the growth and physiology of coffee due to the increased ability of ZnO NPs改善了咖啡的生长和生理机能，对果实和品质的影响比ZnSO更积极₄ to penetrate leaves, and had a more positive effect on fruit and quality than ZnSO4 [Garcia-Lopez等人证明，叶面喷施Garcia-Lopez et al demonstrated, ZnO NPs（ (1000 mg/L和 and 2000 mg/L）可提高哈瓦那辣椒果实的抗氧化能力，并显著改善果实品质[38]。K) sprayed on the lencik等人发现，TiO₂Zaf surface increased the antioxidanOt capacity of NPs处理提高了向日葵的产量和营养参数，但TiO₂NPHabanos pepper fruit and s处理具有潜在毒性，而ZignificanO NPs处理未检测到毒性tly improved the fruit quality[3938]。.Davarpanah等得出结论，叶面喷施较低浓度的B或Zn纳米肥可以促进石榴的产量，且果实的特性不受影响[40]。还有其他研究表明，叶面施用锌纳米肥不仅增加了叶片数量和精油含量，还显著提高了植物的生长、产量和养分含量[41,42,43,44,45,46]。可以看出，叶面施用锌纳米肥对作物产量、品质、养分量和生理参数的改善有正向影响，可能没有潜在的毒性，但需要注意的是，不同植株的最佳浓度差异可能较大。

环境胁迫效应会改变生态系统过程[53]，破坏生态系统平衡，进而破坏与粮食生产相关的环境平衡，可能导致作物减产[54]。重金属、盐碱化、干旱和高温都是对全球作物生产力和质量产生严重影响的关键环境压力源[55]。人们已经寻求各种策略来提高植物承受这些众多环境压力的能力[56]。纳米肥料效率高、释放慢，已成为减轻环境胁迫效应[57\u201258]和促进恶劣环境下作物栽培的合适选择[59\ et al. conclu201260]。多项研究证实了NPded that s对温度胁迫下植物的积极作用，包括提高光合能力[61]和促进生长发育[62]。然而，对热应激的研究还不够;因此，本文介绍了纳米肥料在缓解重金属胁迫、盐胁迫和干旱胁迫中的应用，这些都是目前研究中比较关注的方面。

Hepravy metals are taken up by plants and accuming a lower concentration of B or Zn nano-fertilizer on the leaf surface could promote the yield of pomegranates without affecting the characteristics of the fruit[40].Other stuldies hate in grain crops for human and animal consumption, seriously endangering cropve shown that leaf surface application of zinc nano-fertilizer not only increases the number of leaves and essential oil content, but also significantly improves plant growth and human health, yield and nutrient content [6341,42,43,44,45,6446]. MIt can be seen that leaf surface applicany investigations have suggested that nanoparticles can mitigate heavy tion of zinc nano-fertilizer has a positive effect on the improvement of crop yield, quality, nutrient content and physiological parameters, and there may be no potential toxicity, but it should be noted that the optimal concentration of different plants may vary greatly.

Environmental stress on planteffects will change ecosystem processes [6553],66]. destroy Fecoliar application of Se and Si NPs alleviates mesystem balance, and then destroy the environmental balance related to food production, which may lead to crop yield reduction [54]. Heavy metals, salinization, drought, and high temperatures are all key environmental stress in rice and improves brown rice yield and qualityors that have serious impacts on global crop productivity and quality [55]. Various strategies have been sought to enhance the ability of plants to withstand these numerous environmental stresses [6756]. FNanoliar application of ZnO NPs mitigated Cd contamination and increased plant height and biomass as well as chlorophyll concentr-fertilizer has high efficiency and slow release, and has become a suitable choice to reduce environmental stress effects [57\u201258] and promote crop cultivation in harsh environments [59\u201260]. A number of studies have confirmed the positive effects of NPs on plants under temperature stress, including improving photosynthetic capacity [61] and promoting growth and development [62]. However, heat stress has not been studied enough; Therefore, this paper introduces the application of maize plants [68].nano-fertilizer in alleviating heavy metal stress, salt stress and Fdroliar application ofught stress, which are relatively concerned aspects in current research.

重金属被植物吸收并积累在粮食作物中供人类和动物食用，严重危害作物生长和人类健康[63\u201264]。许多研究表明，纳米颗粒可以减轻植物对重金属的胁迫[65\u201266]。叶面施用硒和硅氮磷钾可缓解水稻的金属胁迫，提高糙米产量和品质[67]。叶面喷施ZnO NPs减轻了Cd污染，提高了玉米植株的株高和生物量以及叶绿素浓度[68]。叶面施用TiO2NPs可显著降低茎畲含量，对降低Cd诱导的毒性有显著贡献;然而，土壤中TiO的施用₂秆She含量，显著降低CD诱导的毒性。然而，在土壤中施用TiO 2NPs增加了玉米在CdD污染土壤中对Cd的吸收[69]。综上所述，在叶片表面施用纳米肥对土壤重金属污染有缓解作用，在一定程度上可能比土壤施用更有用。然而，需要注意的是，重金属的存在可能会促进植物中纳米颗粒的吸收和富集，并产生共毒性，从而，导致食品安全问题[70]。

盐度被认为是限制全球作物产量的主要非生物胁迫之一[71\u201272]。盐胁迫限制了生长，减少了生物量，导致叶绿素降解并改变了水的状态[73]。针对盐胁迫的更环保的缓解策略以提高作物产量对农业部门至关重要[74]。Abdelaal等人证明，叶面施用硅可以通过改善水分状态、提高光合速率、调节某些渗透压和植物激素以及提高增加抗氧化酶活性来减轻，减轻了盐胁迫对甜椒的不利影响[75]。Hajihashemi等人证明，叶面喷施二氧化硅纳米肥料可以通过改善酶和非酶抗氧化系统来显着提高小麦植物的抗盐性[76]。.Perez-Labrada等人认为，叶面施用Cu纳米颗粒通过提高增加Na+/K+比率以及值和刺激植物的抗氧化机制来增强耐盐性[77]。Sheikhalipour等研究证明，叶面施用Cs-Se NPs可以提高叶片光合色素含量，促进植物生产，并通过提高增加SOD、POD和CAT酶的活性来减轻盐胁迫条件活性来减少盐胁迫下的氧化损伤[78]。Mustafa等人发现，叶面施用喷施低剂量TiO2纳米颗粒可改善了小麦的发芽特性以及水分和渗透潜力，并有助于提高植物对盐胁迫的耐受性[79]。此外，一项综述表明，施用Zn和ZnO NPs可以减轻盐胁迫对作物产量和品质的不利影响，并增加蛋白质含量和抗氧化能力[37]。硅纳米硅肥在缓解盐胁迫方面具有发挥积极作用[55,80,81]。例如，Alsaeedi等人的研究结果表明，无定形二氧化硅纳米颗粒（Si NPs）有助于黄瓜植株在盐胁迫下的正常生长，在整个生长季节没有任何明显的缺脱水症状[82]。然而，叶面施用硅肥尚未得到充分研究，是一个新的研究方向。硅纳米颗粒作为喷涂其他纳米颗粒的涂层也相对较新。一项研究表明，叶面施用盐胁迫下，ZnO NPs和ZnOo-Si NPs对盐胁迫下的豌豆植株有不同的影响豌豆植株的叶片施用效果不同[83]。较高浓度的ZnO NPs会可产生一定的植物毒性作用，而ZnOo-Si NPs在生理条件下对植物无毒性，在较高浓度下甚至具有轻微的刺激作用。叶在叶片表面施用纳米肥是缓解盐胁迫的趋势之一。

干旱条件也是制约作物产量的关键因素，导致对植物在的形态、生理和分子水平上经历造成许多不利胁迫[84]，影响植物生长、生理和产量[85]。干旱胁迫通常是干旱诱导的气孔闭合导致氧化应激的结果，进而导致叶绿体和线粒体中ROS的产生增加[86,87]。干旱胁迫通过改变叶绿素和其他光合色素的含量来限制光合过程，从而导致植物停止生长[88,89,90]。此外，随着干旱的恶化，土壤盐碱化和钙化加剧，这反过来又进而导致生产力显着下降[91]。在缺水的半干旱热带地区，叶面施用纳米肥材料可能是提高产量的最佳选择，因为其溶解和被根系吸收需要大量的水它需要大量的水来溶解并被根系吸收[92]。叶面施用纳米肥料作为生长调节剂，可以促进干旱条件下的作物作物的发育和生产力[92]。例如，喷叶面喷施ZnO NPs可以提高产量和作物品质[41,93]以及和种子的营养品质[94]，并改善以及气孔导度和作物干旱胁迫指数[94]。此外，Moitazedi等人发现，叶面施用锌肥可显著改善干旱胁迫对膜稳定指数（MSI）的影响[95]。研究还表明，在缺水条件下，在叶片表面喷施Fe和Zn纳米肥可以改善正常灌溉的豆类下豆类的生理特性和种子产量[85\u201296]。叶面施用K-纳米螯合物可以改善生长、生理生化特性，增加定量和定性性状，减轻水分胁迫的负面影响[97]。在叶片表面施用镁纳米肥和壳聚糖肥可提高叶绿素总产量、种子产量和含油量，并缓解干旱胁迫[98]。除了几种金属纳米肥料外，非金属纳米肥料也已用于许多应用。

综上所述，在非生物胁迫下在叶片表面施用纳米肥可以提高植物酶活性，增强植物抗氧化能力。这些改良可以提高作物对逆境的抵抗力，从而提高产量和质量。