Nanoplastics accumulate in land-plant tissues

Date:
June 22, 2020
Source:
University of Massachusetts Amherst
Summary:
As concern grows among environmentalists and consumers about micro-
and nanoplastics in the oceans and in seafood, they are increasingly
studied in marine environments. But little was known about
nanoplastics in agricultural soils. Researchers now have direct
evidence that nanoplastics are internalized by terrestrial plants.



FULL STORY ==========================================================================
As concern grows among environmentalists and consumers about micro-
and nanoplastics in the oceans and in seafood, they are increasingly
studied in marine environments, say Baoshan Xing at the University of Massachusetts Amherst and colleagues in China. But "little is known about
the behavior of nanoplastics in terrestrial environments, especially agricultural soils," they add.


========================================================================== Xing, an environmental scientist at UMass Amherst's Stockbridge School
of Agriculture, and collaborators at Shandong University, China, point
out that until now, there had been no direct evidence that nanoplastics
are internalized by terrestrial plants.

They state, "Our findings provide direct evidence that nanoplastics
can accumulate in plants, depending on their surface charge. Plant
accumulation of nanoplastics can have both direct ecological effects
and implications for agricultural sustainability and food safety." Both positively and negatively charged nanoplastics accumulate in the commonly
used laboratory model plant, Arabidopsis thaliana.

Xing adds that widespread global use and persistence in the environment
result in an "enormous" amount of plastic waste. He says, "Our experiments
have given us evidence of nanoplastics uptake and accumulation in plants
in the laboratory at the tissue and molecular level using microscopic, molecular and genetic approaches. We have demonstrated this from root
to shoot." Details are in Nature Nanotechnology this week.

Xing points out that nanoplastic particles can be as small as a protein
or a virus. Weathering and degradation change plastic's physical
and chemical properties and imparts surface charges, so environmental
particles are different from the pristine polystyrene nanoplastics often
used in the lab.

"This is why we synthesized polystyrene nanoplastics with either positive
or negative surface charges for use in our experiments." He helped
to design the study, interpret the results, evaluate and revise the
manuscript while a large team at Shandong University led by Xian-Zheng
Yuan and Shu-Guang Wang conducted the experiments.

They grew Arabidopsis plants in soil mixed with differently charged, fluorescently labeled nanoplastics to assess plant weights, height,
chlorophyll content and root growth. After seven weeks, they observed
that plant biomass and height were lower in plants exposed to nanoplastics
than in controls, for example.

"Nanoplastics reduced the total biomass of model plants," Xing adds. "They
were smaller and the roots were much shorter. If you reduce the biomass,
it's not good for the plant, yield is down and the nutritional value
of crops may be compromised." He adds, "We found that the positively
charged particles were not taken up so much, but they are more harmful
to the plant. We don't know exactly why, but it's likely that the
positively charged nanoplastics interact more with water, nutrients
and roots, and triggered different sets of gene expressions. That needs
to be explored further in crop plants in the environment. Until then,
we don't know how it may affect crop yield and food crop safety."
The team also analyzed seedlings to investigate sensitivity of the
roots to charged nanoplastics. Exposed for 10 days, seedling growth was inhibited compared with that of control seedlings. To identify molecular mechanisms responsible, the researchers used RNA-Seq transcriptomic
analyses of roots and shoots, then verified results with a quantitative
PCR assay on three root genes and four shoot genes.

"Regardless of the surface charge, Arabidopsis can take up and transport nanoplastics with sizes of less than 200 nm," they write. Further,
"In this study, we mainly demonstrate that the pathway of uptake and
transport of nanoplastics in root tissues differed between differentially charged nanoplastics."

========================================================================== Story Source: Materials provided by
University_of_Massachusetts_Amherst. Note: Content may be edited for
style and length.


========================================================================== Journal Reference:
1. Xiao-Dong Sun, Xian-Zheng Yuan, Yuebin Jia, Li-Juan Feng,
Fan-Ping Zhu,
Shang-Shang Dong, Jiajia Liu, Xiangpei Kong, Huiyu Tian, Jian-Lu
Duan, Zhaojun Ding, Shu-Guang Wang, Baoshan Xing. Differentially
charged nanoplastics demonstrate distinct accumulation in
Arabidopsis thaliana.

Nature Nanotechnology, 2020; DOI: 10.1038/s41565-020-0707-4 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/06/200622152542.htm

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