Adsorption and translocation of micro and nanoplastics in plants: Myth or measurable process?

Every time we consume a serving of lettuce (Lactuca sativa), wheat (Triticum aestivum), or rice (Oryza sativa), we are interacting with a profoundly altered biogeochemical cycle. Thus, the purpose of this analysis is to break down how the root and leaf systems of crops have ceased to act as an insurmountable barrier.

The intersection of synthetic polymer pollution and food safety has emerged as one of the most complex scientific challenges of our century. For decades, ecological research on microplastics focused on marine ecosystems; however, recent research has led to a paradigm shift. Agricultural soils act as critical reservoirs.

Current evidence compels us to recognize that plants now function as active translocation interfaces, allowing synthetic particles to penetrate millennia-old biological defenses and colonize the base of the human food chain. This massive accumulation, driven by "plasticulture" (the use of mulch films) and the application of sewage sludge, raises a fundamental question: can plants, the base of the human and animal food web, absorb these synthetic particles? Current experimental evidence demonstrates that the answer is yes, although the internalization mechanisms involve profound technical and biophysical complexity (Fig. 1).

Fig. 1: Mechanism of plastic absorption by the plant. Azeem, I. et al. (2021).

Plants have evolved over millions of years to filter nutrients and exclude pathogens using formidable physical barriers, such as the root endodermis and the Casparian strip However, plastics have found multiple ways to circumvent these defenses.

Root Absorption Mechanisms

In real agricultural soils, a plastic fragment does not remain unchanged. It rapidly adsorbs organic matter and proteins from root exudates, forming a dynamic structure called an "eco-crown" or bio-crown . This coating alters the surface charge and hydrophobicity of the polymer, acting as a "biological passport" that tricks plant cell surfaces and facilitates intimate contact with the root epidermis, a very similar mechanism already described in human and animal physiology.

The rhizosphere, the root system of plants, is the main exposure front. Scientific models, supported by an in vitro analysis using confocal microscopy by Zytowski et al. (2024) , indicate that translocation depends critically on particle size and charge. At the nanoscale, particles enter a regime of "exponential reactivity." Their massive surface-to-volume ratio not only increases their surface energy but also alters their bioidentity, allowing them to interact with the lipid bilayers of plant membranes. This reactivity facilitates the crossing of barriers previously considered impenetrable to inert solids. Thus, Particles smaller than 100 nm (nanoplastics) have the ability to move passively through intercellular spaces (apoplastic pathway) or cross into the cell interior (symplastic pathway). A hydroponic study led by Liu et al. (2022) demonstrated that 80 nm polystyrene (PS) nanoparticles can penetrate rice roots and accumulate in the stem xylem and leaf veins.

The root system acts as the primary infiltration interface through 4 distinct mechanisms:

1. Crack-entry (Entrance through cracks): Intact roots are effective filters against larger particles (≥ 1 µm). However, smaller particles can enter through cracks in the areas where lateral roots emerge. where the epidermal cells of the primary root separate to allow the passage of the new root. At these junctions, protective barriers such as the Casparian strip are discontinuous or have not fully formed, allowing plastic particles to passively penetrate the xylem vascular system, driven by the transpiration stream.

2. Split hole (Fracture mechanism): Through oxidative stress fracture, where the accumulation of reactive oxygen species (ROS) induces morphological changes that fracture the protective layer in crops such as corn. This oxidative stress causes the apical epidermal cells to change their morphology, becoming more spherical, which widens the intercellular spaces and fractures the protective layer of the root, creating "holes" through which particles enter unimpeded.

3. Endocytosis (Active Internalization): For particles on the nanoscale Active internalization via endocytic vesicles has been proposed. Although this process has been observed in in vitro cell cultures (such as tobacco BY-2 cells), its relevance in intact plants remains a subject of debate due to the limitations imposed by turgor pressure and the cell wall. This evidence is considered limited and requires further validation under field conditions.

4. Tissue Wounds: A recent study in Nature Communications led by Yin et al. (2026) provided a fundamental direct evidence: deep cuts in taro and maize roots nullify the barrier function, allowing 1-5 µm microplastics to rapidly enter the xylem and accumulate massively in corms and stems.

Absorption of atmospheric xenobiotics

Until recently, soil monopolized scientific attention. However, a review of soil-plant interactions by Chaudhary et al. (2025) in npj Emerging Contaminants and recent studies in high-impact journals reveal that leaves exposed to atmospheric dust can absorb nanoplastics and polyethylene terephthalate (PET) particles through their stomata. Once inside the mesophyll, these particles are transported by the vascular bundles, accumulating to critical concentrations in leafy green vegetables grown outdoors.

At this point, we might ask ourselves… If vegetables absorb microplastics directly from polluted urban air, and outdoor-grown plants have accumulations up to 100 times higher than those in greenhouses, are greenhouses a food security solution, or does the plastic of their own structures become the source of the synthetic rain that bathes the crops? We are thus faced with a genuine food dilemma, since greenhouses represent a critical solution for food security that, simultaneously, acts as a source of persistent pollution due to the fragmentation of their structures into microplastics that are incorporated into the soil-plant system, as evidenced by the review by Serrano-Ruiz et al. (2021) (Fig.2).

Fig 2. On the impacts of plasticulture on agroecosystems. Serrano-Ruiz , H. et al. (2021)

Physiology of Stress and the Trojan Horse

The presence of synthetic polymers in plant tissues is not biologically harmless and reveals detailed phytotoxicity in a cascade of systemic alterations.

At the embryonic level, mechanical blockage of the seminal pores has been evidenced, which drastically delays germination, as evidenced by Bosker et al. (2019) in cress seeds (Lepidium sativum).

Furthermore, at the intracellular level, the particles interfere with chloroplasts and mitochondria. According to Sánchez-Cifuentes et al. (2025) ,this causes the overproduction of Reactive Oxygen Species (ROS). Although the plant mobilizes defense enzymes such as superoxide dismutase (SOD), catalase (CAT), and peroxidase (POD), as well as an increase in malondialdehyde (MDA) levels, the persistence of the xenobiotic usually exceeds the neutralization capacity, resulting in lipid peroxidation of cell membranes. inducing damage to membranes and reducing chlorophyll synthesis, which diminishes biomass and crop yield.

Finally, Due to their hydrophobic nature, plastics act as vectors for co-contaminants. This mechanism, widely recognized and studied by the international scientific community in the fields of environmental toxicology and polymer science, is known as the "Trojan Horse ." Experiments have shown that plastics increase the concentration of drugs like ibuprofen in sprouts by 300% and facilitate the entry of persistent substances such as PFAS. They absorb heavy metals like cadmium (Cd) and pesticides , facilitating their direct transport into the plant and exacerbating the phytotoxicity of edible tissues.

Managing Uncertainties and Analytical Challenges

It is imperative to draw a strict line in the validation of knowledge. While the presence and systemic bioaccumulation of plastics in plants is proven, current data present severe methodological limitations, as almost all the evidence comes from hydroponic or in vitro trials with massive doses of virgin polystyrene microspheres. Extrapolating this to the (much lower) environmental concentrations and complex mixtures of real agricultural soil remains a critical gap.

The main bottleneck for current regulation is not a lack of evidence, but analytical standardization. The scientific community must decide between the sensitivity of pyrolysis-GC-MS (total mass) versus the morphological precision of micro-Raman spectroscopy in order to establish legally binding safety limits. Detecting nanoparticles within a biological matrix is an unresolved analytical challenge, as highlighted in a comprehensive review published by Yu et al. (2024) .

Conclusions and Open Lines of Research

The plant barrier has been breached. If we thought plants were pure filters, they are not; they act as active participants and vectors in the biogeochemical cycle of plastic, channeling these pollutants, although we do not yet know to what extent, into the human diet.

Given the certainty that our crops are systemically internalizing synthetic residues, even though we don't truly know the extent of the problem, are we prepared to redefine food safety standards in an irreversibly plasticized world? The scientific challenge of the next decade will not only be to measure what enters the root zone, but to redesign our agri-food systems before the damage becomes irreversible.

The presence of polymers in edible parts directly links environmental degradation with public health, and curbing this threat requires the urgent standardization of ultra-high resolution analytical protocols.

Emilio J. Orovengua

Biochemist | Science Communicator | Microplastic Specialist