Nanomaterial-Mediated Alleviation of Abiotic Stress in Plants: Mechanisms and Applications

Abstract

Drought, salinity, heavy metal contamination and temperature fluctuations are increasingly constraining crop production. Conventional agronomic and chemical approaches alone often fail to ensure stable yields under these abiotic stresses. Nanomaterials are emerging as complementary tools for improving stress tolerance and helping to stabilize yield because they can interact efficiently with key processes at the rhizosphere, at the leaf surface and within cells. Their high surface area, tunable surface chemistry and functionalization, and controlled-release properties make them suitable for root application, foliar spraying, and seed treatment. These features enable low-dose, efficient, and targeted delivery. This review delineates five mechanistic dimensions: restoring redox homeostasis; enhancing nutrient uptake and maintaining ion balance; modulating signaling factors and hormone levels; influencing gene expression; and improving structural and physiological traits at the root and chloroplast levels. Based on case studies under salinity, drought, and heavy metal conditions, we summarize material- and route-dependent differences in efficacy and define dose boundaries. Moreover, the current limitations arising from limited field evidence and nonuniform evaluation standards are also highlighted. Accordingly, we outline key considerations for material design and application assessment, underscoring the value of this review in integrating mechanisms and guiding the practical translation of nanomaterials for stress alleviation in plants.

1. Introduction

The Food and Agriculture Organization of the United Nations (FAO) indicated that the global population could reach 10 billion by 2050 [1]. To feed this growing population, the sharp rise in food demand will require a 70% increase in crop productivity [1]. However, global agriculture is facing increasingly severe abiotic stresses, including prolonged drought, soil salinization, heavy metal contamination, and ever more frequent extremes of high and low temperature [2]. These stresses often occur alone or in combination, posing serious threats to plant metabolism, nutrient uptake, membrane stability, and yield formation, ultimately leading to reduced crop yields and quality deterioration [3]. To address these challenges, research and production practices have long relied on multiple strategies, including chemical regulation, genetic breeding, and agronomic management. Chemical regulators help stabilize plant physiological processes under stress [4,5]; genetic breeding introduces key resistance traits into elite cultivars [6,7]; and agronomic practices optimize water, nutrient, and soil conditions to support crop performance in adverse environments [8]. These approaches have played essential roles in sustaining agricultural production. However, each is affected by intrinsic constraints such as long breeding cycles, environmental concerns associated with repeated chemical inputs, or reduced efficacy under increasingly variable climate conditions [2,4,6]. As global agriculture faces more frequent and complex stress scenarios, there is growing interest in developing additional, complementary technologies. This has encouraged exploration of new technologies to enhance plant resilience and support sustainable crop production.

Against this backdrop, the rapid advancement of nanotechnology offers unprecedented opportunities for managing agricultural stress. Engineered nanomaterials exhibit advantages that are difficult to achieve with traditional materials due to their unique nanoscale effects, such as high specific surface area, active surface functional groups, and tunable physicochemical properties [3]. Firstly, their nanoscale size and surface reactivity allow nanomaterials to access stress-sensitive sites and modulate key processes in situ, for example, scavenging excess reactive oxygen species (ROS), buffering toxic ions, and stabilizing membranes, thereby preserving photosynthesis and water-use efficiency under salinity or drought [9,10,11]. In addition, nanomaterials enable controllable release: protective cargos such as osmoprotectants, signaling modulators, or micronutrients can be encapsulated and released in a programmed fashion, triggered by pH, redox state, enzymatic activity, or moisture dynamics associated with stress [12]. This timing control lowers the required dose, prolongs efficacy, and aligns protection with stress peaks [2]. Separately, nanomaterials support targeted delivery. By tuning particle size, surface charge, and ligand functionalization, they can preferentially accumulate at specific tissues or cell types, such as root epidermis, guard cells, or chloroplasts, thereby increasing on-site bioavailability and reducing off-target effects [13,14]. Therefore, elucidating the mechanisms and application prospects of nanomaterial-mediated stress alleviation in plants represents both a key frontier at the interface of stress biology and nanoscience and a potential breakthrough for advancing sustainable agriculture under climate change.

Despite growing evidence that nanomaterials can markedly alleviate abiotic stress in plants, their mechanisms of action remain insufficiently understood in a systematic sense. Current experiments are mostly confined to a few crops under single-stress conditions, lacking an integrative view across mechanisms and levels of organization. For example, studies on how nanomaterials directly scavenge excessive ROS or restore redox balance by inducing antioxidant enzyme systems are still scattered, making it difficult to quantify their generalizable effects across stress types [15]. Likewise, although some nanomaterials have been shown to enhance mineral nutrient uptake and mitigate Na⁺ or heavy metal toxicity, the long-term impacts and the underlying logic of ion homeostasis remain unresolved [16]. At the signaling level, interactions between nanomaterials and key plant hormones, such as abscisic acid (ABA), indole-3-acetic acid (IAA), salicylic acid (SA), and jasmonic acid (JA), are complex, and findings are often inconsistent; whether nanomaterials optimize stress responses by integrating signaling networks is still largely unknown [17]. Furthermore, while effects on gene expression, epigenetic modifications, and transcription factor networks have been reported, the mechanistic chain is incomplete. Even at morphological and physiological levels, reports that nanomaterials improve chloroplast ultrastructure, photosynthetic performance, and the accumulation of osmolytes remain largely descriptive, with limited cross-system mechanistic analysis. These gaps constrain the scientific application of nanotechnology in agriculture and underscore the need for systematic integration across five dimensions—redox regulation, nutrient uptake, signaling modulation, molecular control, and structural/physiological improvement. Accordingly, this review synthesizes recent advances to construct an overall framework for nanomaterial-mediated stress alleviation in plants and links mechanisms with applications and future directions to support translation into sustainable agricultural practice.

This review first outlines the distinctive properties and advantages of nanomaterials in agricultural applications, and then focuses on the multilevel mechanisms involved in alleviating abiotic stresses, including redox regulation, nutrient uptake and ion homeostasis, signaling molecules and hormone regulation, gene- and molecular-level control, and structural and physiological improvements. Building on this, we synthesize representative application cases and practical explorations, analyze their potential value and real-world bottlenecks, and discuss key challenges such as ecological safety, scalable production, and standardized evaluation. Finally, in light of emerging trends and the needs of sustainable agriculture, we propose future directions. Through this logical framework, the review aims to provide a systematic summary and fresh perspectives for advancing nanomaterials in plant stress-resilience research and their translation to agricultural practice.

2. Properties and Routes of Nanomaterials for Alleviating Abiotic Stress in Plants

Nanomaterials exhibit distinct advantages in mitigating abiotic stresses in plants, owing to their compositional diversity, tunable physicochemical properties, and multiple interaction pathways with plants (Figure 1). Commonly used nanomaterials include metal and metal-oxide nanoparticles (e.g., ZnO, TiO₂, Fe₃O₄), carbon-based nanomaterials (e.g., carbon nanotubes, graphene oxide, carbon quantum dots), silicon-based nanomaterials, and various functional polymer nanocomposites [5,15,18]. These materials exhibit distinct functionalities that are closely linked to their composition. Metal and metal-oxide nanoparticles can optimize ion homeostasis, enhance light-use efficiency, and serve as micronutrient sources [1,16]. Carbon-based nanomaterials act as efficient molecular carriers and are useful for targeted delivery and modulation of signal transduction [19,20]. Silicon-based nanomaterials are known for their biocompatibility and for strengthening cell wall structure while reducing osmotic stress [15]. Compared with conventional materials, nanomaterials offer notable benefits in particle size, specific surface area, and surface functional groups. Their ultrafine size confers superior tissue penetration and interfacial reactivity. The high surface area enhances adsorption, catalytic capacity, and signaling modulation. Additionally, the diverse surface functionalities enable interactions with biomacromolecules.

As shown in Figure 2, nanomaterials can enter plants via multiple routes. Root uptake is the most direct pathway. Nanoparticles move from the rhizosphere across the epidermis and cortex. Then pass through cell walls and apoplast/symplast interfaces. After entering the xylem, they are carried upward with the transpiration stream. During this process, they often accumulate at lateral root zones and root hairs, where tissue permeability is higher [21]. Foliar spraying allows nanomaterials to enter rapidly through stomata, cuticular microchannels, and wounds. Then they move through the apoplast and, in some cases, are loaded into the phloem for bidirectional transport. Retention and penetration are strongly influenced by droplet formulation, the use of surfactants, and the hydrophobic or hydrophilic nature of the particles [22]. Seed priming or coating deposits nanomaterials on the seed surface or in the perisperm/seed coat matrix, where they are mobilized during imbibition and early radicle/coleoptile emergence, conferring early-stage stress tolerance and shaping the seedling ionome and antioxidant status [23]. These routes differ in efficiency, spatial distribution, transport directionality (xylem- versus phloem-dominant), and duration of action. These differences are further influenced by particle size, charge, aspect ratio, and surface functionalization. Biological factors, including plant species and developmental stage, also play important roles in shaping uptake and transport behaviors [21]. Collectively, this diversity in entry and movement provides considerable flexibility in plant–nanomaterial interactions and allows applications to be tailored to specific stress conditions and management goals.

3. Nanomaterial-Mediated Mechanisms of Stress Tolerance

The anti-stress effects exerted by nanomaterials can be summarized as a five-layer interactive framework [24,25]: first, front-end redox regulation rapidly alleviates ROS pressure; second, nutrient uptake and ion homeostasis are restored; third, signaling molecules and hormone regulation act synergistically to amplify and allocate responses; fourth, transcriptional and epigenetic programs are reshaped at the gene and molecular levels; and finally, structural and physiological improvements manifest as optimized root and chloroplast architecture, regulated stomatal behavior and water use, and enhanced osmotic adjustment, as shown in Figure 3.

3.1. Redox Regulation

Under abiotic stresses such as drought, salinity, heavy metals, and extreme temperatures, ROS rapidly accumulate in plant cells. If not promptly scavenged, excessive ROS can peroxidize membrane lipids, denature proteins, and damage DNA, leading to metabolic disruption and even programmed cell death [26]. Thus, maintaining intracellular redox homeostasis is fundamental to stress adaptation in plants. Recent studies indicate that nanomaterials can mitigate oxidative pressure and modulate ROS through multiple routes. On the one hand, certain metal and metal-oxide nanoparticles (e.g., cerium oxide nanoparticles, TiO₂ nanoparticles) as well as carbon quantum dots possess enzyme-mimicking activities due to their unique surface electronic structures, enabling them to simulate superoxide dismutase (SOD), catalase (CAT), or peroxidase (POD) functions and directly catalyze the conversion of ROS such as O₂•⁻ and H₂O₂ [27,28]. On the other hand, nanomaterials can modulate intracellular signaling to induce the plant’s endogenous antioxidant system, reflected by increased activities of key enzymes, together with elevated levels of non-enzymatic antioxidants such as reduced glutathione (GSH) and ascorbate (AsA) [24,26]. This reinforcement of endogenous defenses can be relatively persistent, helping plants sustain metabolic balance under prolonged stress. Notably, compared with conventional chemical antioxidants, nanomaterials offer the advantage of penetrating distinct cellular compartments (e.g., apoplast, cytosol, chloroplasts, mitochondria, peroxisomes) and achieving coordinated scavenging across multiple subcellular levels, thereby reducing both local and global oxidative damage [29,30]. However, in-depth understanding of how different classes of nanomaterials couple with the ROS metabolic network remains limited; their specificity and stability under long-term or combined stress scenarios are still debated, posing a key bottleneck for broader agricultural application.

3.2. Nutrient Uptake and Ion Homeostasis

Under abiotic stress, plant nutrient acquisition and ion distribution are often severely perturbed. For example, salinity drives excessive Na⁺ influx and suppresses K⁺ uptake [31]; drought limits the normal transport of water and mineral elements [10]; and heavy metal contamination causes competitive inhibition of essential elements and toxic accumulation [28]. Thus, sustaining nutrient uptake efficiency and ion homeostasis is integral to plant stress tolerance. Nanomaterials play distinctive roles in this process. Studies show that certain metal and metal-oxide nanoparticles can serve as direct micronutrient sources (e.g., ZnO supplying Zn²⁺, Fe₂O₃ supplying Fe³⁺) and enhance rhizosphere ion-exchange activity to promote nutrient acquisition [31]. Carbon-based nanomaterials are frequently reported to improve root architecture and activity, thereby enhancing water and mineral uptake and, to some extent, modulating transmembrane ion transport [28,32]. Silicon-based nanomaterials, by depositing in cell walls and the apoplast, help restrict excessive Na⁺ entry and maintain a favorable cellular K⁺/Na⁺ ratio, strengthening homeostatic regulation under salinity [33]. In addition, polymer nanocomposites, owing to their robust controlled-release behavior, can deliver nutrients on demand under stress, improving fertilizer use efficiency and reducing losses [34]. Overall, nanomaterials act through multiple routes—supplementing essential elements, modulating ion channel/transporter activity, improving the rhizosphere microenvironment, and mediating controlled release—to jointly sustain nutrient acquisition and ion homeostasis under stress. However, most existing evidence comes from short-term pot or seedling studies. Systematic understanding of nutrient dynamics and potential ecological risks associated with long-term nanomaterial use across diverse crops and soils remains limited, indicating that deeper mechanistic elucidation and application-oriented validation are still needed.

3.3. Signaling Molecules and Hormone Regulation

Plants rapidly perceive external stimuli under adverse environments and regulate downstream responses via signaling molecules and hormonal pathways—one of the core mechanisms of stress tolerance. Evidence indicates that nanomaterials can modulate this complex network through multiple modes. On the one hand, nanoparticles may act as novel signal sources or mediators by shaping the dynamics of small-molecule signals such as reactive oxygen species (ROS) and nitric oxide (NO), thereby influencing intracellular response pathways. For example, appropriate levels of ROS and NO are not only by-products of stress damage but also signals that trigger downstream defenses; the involvement of nanomaterials enables finer tuning of these signal oscillations [35,36]. On the other hand, nanomaterials have been widely reported to alter plant hormone levels, such as promoting abscisic acid (ABA) biosynthesis to enhance stomatal closure and water retention; increasing indole-3-acetic acid (IAA) to improve root architecture; or modulating the accumulation of salicylic acid (SA) and jasmonic acid (JA) to activate defense-related genes [37]. These hormonal changes often couple with variations in signaling molecules, forming network effects that optimize energy allocation and coordinate defense responses under stress [2]. Notably, the roles of nanomaterials in signaling and hormone regulation may be direct or indirect—for instance, via altered nutrient acquisition or metabolic balance. However, how different classes of nanomaterials selectively affect specific signaling pathways, and whether their regulation exhibits tissue specificity or dose dependence, remains insufficiently elucidated [2]. Therefore, although current studies highlight the potential of nanomaterials in modulating signaling molecules and hormones, the spatiotemporal characteristics of their mechanisms remain a key frontier for exploration.

3.4. Gene- and Molecular-Level Regulation

Under adverse conditions, the establishment of plant stress tolerance strongly depends on multilayered regulation of gene expression, including activation of transcription factors, rewiring of signaling-pathway genes, and induction of downstream defense-related genes. Increasing evidence shows that nanomaterials participate deeply in this molecular regulation. On one hand, specific types of nanoparticles can upregulate stress-related genes—those involved in antioxidant defense, ion transport, heat-shock protein synthesis, or osmotic adjustment—thereby enhancing cellular adaptation under stress [9,24]. On the other hand, nanomaterials may modulate gene expression via epigenetic mechanisms, such as altering DNA methylation or histone modifications, which in turn affect chromatin accessibility and transcriptional activity [26,29]. These effects suggest that nanomaterials are not only modulators of physiological processes but may also directly or indirectly engage with genetic and epigenetic regulatory networks. In addition, several studies report that nanomaterials influence key transcription factors, including families associated with abscisic acid (ABA), salicylic acid (SA), or jasmonic acid (JA) signaling, thereby integrating multiple defense cues at higher regulatory nodes [33,37]. Nonetheless, most current findings remain at the transcript-level observation stage; the upstream triggers, material-specific differences, and systems-level impacts on the transcriptome and proteome are still insufficiently resolved. Future integration of multi-omics approaches, coupled with cross-validation against nanomaterial physicochemical properties and bio-interaction modes, will be critical for elucidating precise mechanisms of gene- and molecular-level regulation.

3.5. Structural and Physiological Improvements

Beyond molecular and signaling effects, nanomaterials also induce notable changes in plant structure and physiology, thereby improving overall stress resilience. Studies have shown that appropriate nanoparticle doses can promote root growth and branching and enhance root hair development and activity, which not only strengthens water and nutrient acquisition but also improves resource capture under drought and salinity [26]. At the leaf level, certain nanomaterials optimize chloroplast ultrastructure, maintain thylakoid integrity and chlorophyll content, and help sustain relatively high photosynthetic efficiency under stress. Nanomaterials have also been reported to induce osmotic adjustment, increasing the accumulation of osmolytes such as proline, soluble sugars, and compatible solutes (e.g., glycine betaine), thereby supporting water balance and membrane stability [29]. In addition, silicon-based or metal-oxide nanomaterials deposited in cell walls and epidermal layers can reinforce tissue mechanical strength and barrier functions, reducing the risk of pathogen ingress or excessive salt ion penetration [18,20,22]. Overall, these structural and physiological improvements are intertwined with the previously described maintenance of redox homeostasis, ion balance, and signaling regulation, collectively shaping integrated stress tolerance. However, current evidence remains largely phenotypic. Systematic and quantitative studies are still lacking regarding organ-specific and developmental-stage-specific responses to various nanomaterials, as well as potential long-term side effects, posing challenges for their safe and efficient application in agricultural production.

4. Application Cases and Practical Exploration

In recent years, with the rapid advancement of nanobiotechnology in agriculture, the application of nanomaterials in alleviating plant abiotic stress has progressed from phenotypic observation to mechanistic elucidation. Nanomaterials with different structures, compositions, and surface modifications exhibit material-specific mitigation mechanisms, offering diverse routes to enhance crop stress tolerance, as summarized in Table 1.

For example, a chitosan–selenium (Cs–Se) nanocomposite could efficiently scavenge reactive oxygen species (ROS) via enzyme-mimicking activity, activate the MAPK signaling pathway, and reshape rhizosphere microbial communities, thereby markedly alleviating salt stress-induced oxidative damage and ion disequilibrium in rice and pak choi [31]. By contrast, graphene oxide (GO) primarily operates through physical adsorption and regulation by hydrophilic surface groups to improve water uptake and ion-barrier function of seeds under salinity, increasing germination rates of Persian clover and highlighting the potential of carbon-based nanomaterials at the seed stage [38].

Under drought stress, poly(acrylic acid)-coated Mn₃O₄ nanoparticles (PMO) not only display ROS-scavenging nanozyme activity but also regulate guard cell ROS levels to maintain moderate stomatal aperture, thereby improving photosynthetic performance and water-use efficiency in cotton—significantly outperforming conventional Mn ion treatments and underscoring the unique advantages of nanostructures in stomatal regulation [39]. At the cellular level, non-invasive micro-test technology combined with transcriptomics showed that CeO₂ nanoparticles activate the Na⁺–GIPC sensing–Ca²⁺ signaling–SOS1 efflux pathway to promote efficient Na⁺ extrusion; in contrast, N-doped carbon dots (N-CDs) induce NHX1 expression and vacuolar Na⁺ sequestration, accompanied by transient K⁺ signaling, indicating that distinct nanomaterials can engage fundamentally different ion-homeostasis mechanisms in plant cells [40]. In addition, low concentrations of SiO₂ nanoparticles enhance antioxidant enzymes such as glutathione peroxidase (GPX) and superoxide dismutase (SOD), induce stress-related proteins, and significantly mitigate NaCl-induced growth inhibition, suggesting promising applications of silicon-based nanomaterials in tuber crops [41].

Although most mechanistic studies are still conducted under controlled or greenhouse conditions, an increasing number of field-scale trials are now testing nano-enabled strategies under realistic production environments. In mildly Cd-contaminated paddy fields, researchers carried out a multi-site field experiment using a recyclable lignin hydrogel loaded with FeS nanoparticles (FHC) [4]. After one or two rice-growing seasons, a single round of FHC application reduced soil Cd by 0.42–31.7% and grain Cd by 1.5–49.1%. Two consecutive rounds produced cumulative soil Cd reductions of up to about 50%, without detectable negative effects on rice biomass or yield [4]. Based on these results, a practical application scheme was proposed: about 500 kg ha⁻¹, one mesh bag per m², applied 1–2 weeks after transplanting and removed before harvest. A preliminary economic analysis suggested that such nano-enabled, recoverable amendments can support “remediation while producing” in Cd-polluted paddies. In another study, multilocational field trials were conducted in three paddy fields with low, moderate and high Cd contamination [42]. Rhizosphere injection of ball-milled zero-valent iron nanoplates (100–1000 mg kg⁻¹) at the grain-filling stage significantly reduced Cd in brown rice to below the national food-safety limit. The 100 mg kg⁻¹ treatment also increased yield and thousand-kernel weight and showed negligible effects on soil microbial diversity. These field studies demonstrate that nanomaterial-based interventions can be designed as field-feasible and crop-compatible tools that improve food safety while maintaining productivity. At the same time, they highlight that robust field evidence is still available only for a few contaminants, crops and regions, and that broader, standardized field validation is urgently needed.

Despite these benefits, several important risk factors remain insufficiently resolved, including dose-dependent toxicity, long-term ecological safety and the complexity of interactions within the crop–soil–microbiome system. For example, Se- or Mn-based nanomaterials can improve antioxidant capacity at low doses, but they have also been reported to cause growth inhibition, oxidative damage or nutrient imbalance at higher concentrations in crops such as wheat and rice [31,39]. Some metal-oxide nanomaterials, such as CuO and ZnO nanoparticles, show similar dual effects [1,16]. The environmental fate and degradation of carbon-based nanomaterials (e.g., carbon nanotubes and graphene derivatives) are still uncertain. Several studies suggest that repeated applications may alter soil microbial community structure and enzyme activity [20,32]. These findings point to possible accumulation in soil and water, trophic transfer along food chains, and unintended effects on non-target organisms, all of which require careful assessment. Addressing these issues will require not only more mechanistic insight but also long-term, field-relevant data. A more balanced evaluation of both benefits and risks is therefore essential before large-scale deployment of nano-enabled technologies in agriculture.

Table 1. Nanomaterial-based mitigation of plant abiotic stress: a comparative summary.

Nanomaterial	Target Plant	Application Purpose	Treatment Method	Key Advantages	Potential Drawbacks	Reference
Chitosan–selenium nanomaterials (Cs–Se NMs)	Rice (Oryza sativa L.), Pakchoi (Brassica chinensis L.)	Alleviate salt stress (100 mM NaCl)-induced oxidative damage and enhance plant growth	Root application, 100–500 mg/L (optimal: 300 mg/L)	Effectively scavenges ROS and enhances antioxidant enzyme activity, improving plant growth and salt tolerance.	High Se content may cause phytotoxicity; long-term soil impacts need further study.	[31]
Graphene Oxide (GO)	Persian clover (Trifolium resupinatum L.)	Mitigate salt stress’s impact on seed germination	Seed exposure to GO (0–500 mg/L) with/without NaCl (−0.1 MPa)	Effectively improves germination rate and seedling growth under saline conditions.	Limited understanding of long-term phytotoxicity and environmental fate.	[38]
Silicon dioxide nanoparticles (SiO2-NPs)	Potato (Solanum tuberosum L.) cv. Sante & Proventa	Alleviate salt stress (50 & 100 mM NaCl) and improve in vitro and greenhouse growth	Foliar spray at 50 & 100 mg L−1 (optimal: 50 mg L−1)	Enhances growth and antioxidant enzyme activity (GPX, SOD), and induces stress-related protein expression.	High concentration (100 mg L−1) may become phytotoxic and reduce beneficial effects.	[41]
PAA-coated Mn3O4 nanoparticles (PMO)	Cotton (Gossypium hirsutum L.)	Enhance drought tolerance by ROS scavenging and stomatal regulation	Foliar spray (200 mg/L)	Improves biomass, photosynthesis, and ROS homeostasis under drought	Limited data on long-term environmental impact	[39]
nCeO2 and N-CDs	Tobacco BY-2 suspension cells	Enhance salt tolerance via Na+ extrusion or sequestration	Exposure in culture medium (0.1 mg/L nCeO2; 0.5 mg/L N-CDs)	nCeO2 promotes Na+ efflux via SOS pathway; N-CDs enhance vacuolar Na+ sequestration	Mechanism specificity unclear; effects may vary by plant species	[40]

Table 1. Nanomaterial-based mitigation of plant abiotic stress: a comparative summary.

Nanomaterial	Target Plant	Application Purpose	Treatment Method	Key Advantages	Potential Drawbacks	Reference
Chitosan–selenium nanomaterials (Cs–Se NMs)	Rice (Oryza sativa L.), Pakchoi (Brassica chinensis L.)	Alleviate salt stress (100 mM NaCl)-induced oxidative damage and enhance plant growth	Root application, 100–500 mg/L (optimal: 300 mg/L)	Effectively scavenges ROS and enhances antioxidant enzyme activity, improving plant growth and salt tolerance.	High Se content may cause phytotoxicity; long-term soil impacts need further study.	[31]
Graphene Oxide (GO)	Persian clover (Trifolium resupinatum L.)	Mitigate salt stress’s impact on seed germination	Seed exposure to GO (0–500 mg/L) with/without NaCl (−0.1 MPa)	Effectively improves germination rate and seedling growth under saline conditions.	Limited understanding of long-term phytotoxicity and environmental fate.	[38]
Silicon dioxide nanoparticles (SiO2-NPs)	Potato (Solanum tuberosum L.) cv. Sante & Proventa	Alleviate salt stress (50 & 100 mM NaCl) and improve in vitro and greenhouse growth	Foliar spray at 50 & 100 mg L−1 (optimal: 50 mg L−1)	Enhances growth and antioxidant enzyme activity (GPX, SOD), and induces stress-related protein expression.	High concentration (100 mg L−1) may become phytotoxic and reduce beneficial effects.	[41]
PAA-coated Mn3O4 nanoparticles (PMO)	Cotton (Gossypium hirsutum L.)	Enhance drought tolerance by ROS scavenging and stomatal regulation	Foliar spray (200 mg/L)	Improves biomass, photosynthesis, and ROS homeostasis under drought	Limited data on long-term environmental impact	[39]
nCeO2 and N-CDs	Tobacco BY-2 suspension cells	Enhance salt tolerance via Na+ extrusion or sequestration	Exposure in culture medium (0.1 mg/L nCeO2; 0.5 mg/L N-CDs)	nCeO2 promotes Na+ efflux via SOS pathway; N-CDs enhance vacuolar Na+ sequestration	Mechanism specificity unclear; effects may vary by plant species	[40]

5. Future Directions and Outlook

Nanomaterials show strong potential to improve crop tolerance to abiotic stress, but their long-term use and overall sustainability still need careful study. Future work should clarify how physicochemical traits translate into biological effects, with clear links between particle size, shape, surface chemistry, and their interactions in plants. At the same time, the development of environmentally benign and biodegradable nanocomposites can lower risks of environmental accumulation and improve acceptance in field applications. Combining multiomics with multiscale analyses will help reveal how nanomaterials engage stress-response networks over time and provide a basis for precise use in practice. On the practical side, priority should be given to field trials across a range of crops, soils, and climates, and to refining application methods, rates, and timing so that laboratory findings can move into production. Integrating tools from mechanics, materials science, and information technology, for example, in situ sensing and data guided control, can enable real-time monitoring and fine tuning of effects at the field scale. Finally, broader adoption will depend on policy, cost, and social acceptance; clear regulation and risk assessment will be essential to ensure safe, controllable, and sustainable use. Overall, the outlook is positive, but realizing the benefits of nanomaterials in stress mitigation will require coordinated efforts across disciplines and careful evaluation from controlled experiments to long-term field applications.

6. Conclusions

Owing to their unique physicochemical properties, nanomaterials offer new avenues for helping plants cope with abiotic stresses. This review outlines the basic characteristics of different classes of nanomaterials and systematically summarizes their multifaceted mechanisms of action, including maintenance of redox homeostasis, enhancement of nutrient uptake and ion balance, modulation of signaling and hormones, regulation at gene and molecular levels, and improvements in structure and physiology. Drawing on representative crop cases and practical explorations, we highlight their positive effects in mitigating salinity–alkalinity, drought, and heavy metal stress. At the same time, we identify key remaining gaps, such as incomplete mechanistic clarification, limited field evidence, and uncertain long-term environmental impacts and safety. Looking ahead, progress in nanoagriculture will require interdisciplinary collaboration, advancing stepwise from materials design and mechanistic decoding to field application and governance, in order to balance efficiency, environmental stewardship, and economic viability. Overall, nanomaterials present important opportunities to enhance crop stress tolerance and promote sustainable agriculture, yet their large-scale deployment will depend on rigorous scientific validation and comprehensive risk assessment.