Plastic particles enter wheat and tomato plants and stunt growth

Researchers have discovered that plastic particles can enter wheat and tomato plants, restricting their growth. The findings position agricultural soil as one route by which plastic may enter the food system.

In silty loam soil, wheat and tomato roots retained the larger plastic particles, while smaller particles travelled further down through the soil.

Where plastic particles end up

A research team headed by Dr. Shima Ziajahromi at Griffith University examined how plastic particles move through crops in conditions designed to resemble farmland.

Their work showed that plastic accumulated around plant roots, while some of the smallest particles made their way into plant tissue.

At Griffith’s Australian Rivers Institute, an environmental research centre, Dr. Ziajahromi investigated weathered plastics similar to those already degrading in agricultural soils.

This makes the results relevant to the contamination that crops are likely to encounter, although it does not resolve the more difficult issue of which plants suffer most as plastic accumulates.

Tomatoes suffer the greatest effects

Tomato plants experienced more severe harm than wheat when fibrous plastic collected around their roots.

Under the most severe treatment, tomato shoot growth fell by 67 percent, roots declined by 47 percent, and root biomass decreased by 82 percent.

Wheat was less vulnerable, although its total root length still declined by 39 percent under the high-fibre treatment.

Such reductions are significant because shorter roots take up less water and fewer nutrients, limiting the resources available for plant growth.

Fibres congest the roots

Fibres were particularly notable because their long strands became tangled more readily than fragments among root hairs and the surrounding soil.

This physical obstruction probably disrupted water and nutrient uptake, beginning as a straightforward mechanical issue before developing into wider plant stress.

Chlorophyll, the green pigment responsible for capturing light, also declined most markedly in plants exposed to fibres.

“We also found that plants can trap MPs in the soil, reducing their movement in the environment, but this may also lead to accumulation around roots,” said Dr. Ziajahromi.

Mixed particles worsen the damage

Plastic pollution on farmland seldom consists of a single type of particle, and tomato plants reflected this more complex situation.

When microplastics were combined with smaller particles, tomato shoots declined by 47 percent and roots by 27 percent.

This result suggests additive or synergistic damage, in which different plastics can intensify stress rather than operating independently.

Wheat once more displayed less pronounced effects, indicating that crop species and root structure may shape which plants are most severely affected.

Plastic particles inside stems and leaves

The most concerning finding involved the smallest debris, which travelled from the soil into living plant tissue.

These particles were nanoplastics, fragments small enough to pass through barriers that block larger pieces.

In both crops, aged nanoplastics reached the roots and stem bases; in tomatoes, they were also detected in leaf vascular tissue.

After entering the plant, they may be carried upwards through its water-transport system, meaning their presence in leaves indicates internal movement rather than contamination on the surface.

Ageing alters the risk

New plastic beads acted differently from weathered particles, a contrast that may help explain why older pollution presents a greater concern.

The researchers detected uptake of aged nanoplastics but not pristine particles, implying that worn surfaces interact with roots in different ways.

Sunlight, abrasion and oxidation may change the chemistry of a particle’s surface, affecting how it clumps together, travels and adheres.

Consequently, real-world exposure is determined not just by particle size, but also by the length of time plastic has been degrading.

Why some plastics repeatedly appear

The finding was especially striking because the concentrations matched those measured in fields treated with sewage sludge, the solid residue from wastewater treatment that is often applied as fertiliser.

A 2026 field survey in Southern Ontario, Canada, found that soils amended with biosolids contained, on average, around three times as many microplastic particles as neighbouring untreated fields.

Textile fibres are important in this context because washing clothes releases vast numbers of strands, many of which survive wastewater treatment.

This helps account for the repeated presence of fibrous plastics, particularly polyester, in land used to grow crops.

Crops beyond wheat and tomato

Research involving other crops has already established that edible plants can take up plastic through multiple pathways.

A 2026 study detected nanoplastics in the roots, leaves and edible tissues of lettuce, carrots and wheat.

That research found considerably stronger movement from roots to leaves in lettuce than in wheat or carrots.

The tomato findings broaden this pattern, suggesting that concerns about plastics entering food cannot be attributed to one unusual crop.

Food safety implications

These findings do not demonstrate that people are already consuming harmful quantities of plastic through tomatoes or wheat.

The study did not measure particles in edible fruit, nor could it yet quantify every nanoplastic contained within plant tissue.

Nevertheless, the movement of particles from soil into stems and leaves bridges part of the divide between environmental contamination and human exposure.

“These findings demonstrate that agricultural soil is not just a sink for plastics, but a pathway into the food systems, meaning they could end up on our plates,” said Dr. Ziajahromi.

Farmers, waste managers and regulators must now confront a more difficult reality: plastic in soil can hinder crop growth, accumulate around roots and enter plants.

The next stage is to determine whether weathered nanoplastics reach edible tissues by harvest, and to identify which plastic inputs should be reduced first.