Our Tiny Allies in Toxicological Testing Part 3 – Small Flowering Plants as Alternative Models
By Aaradhya Diwan | March 12th, 2026
Environmental toxicology relies heavily on animal-based models to evaluate the effects of chemical substances on human health and ecological systems. Vertebrate organisms, including rodents, rabbits, and fish, continue to dominate regulatory testing frameworks, as their biological processes are often considered comparable or translatable to those of humans and used to establish regulatory thresholds for environmental exposure.
Recent efforts to Replace, Reduce, and Refine the use of vertebrate animals in toxicology have expanded the use of New Approach Methodologies (NAMs), which include a growing set of alternative assays validated by international and U.S. regulatory bodies. Previous posts in this series examined how non-mammalian animal models, such as transparent roundworms and young zebrafish, can function as effective NAMs by providing insight into toxicity at the developmental, reproductive, and cellular levels while reducing reliance on traditional animal testing.
Despite these advances, much of regulatory toxicology continues to prioritize animal-based systems when assessing the environmental impact of chemical substances. This focus narrows the conceptualization of toxicity, often emphasizing organism-specific outcomes rather than broader biological responses to environmental exposure. Terrestrial plants, which are directly exposed to contaminants in soil, water, and air, represent a critical class of biotic systems for evaluating how chemicals move through and affect ecosystems, with implications that may extend beyond environmental health to inform mechanisms relevant to human exposure.
This article will explore Arabidopsis thaliana's potential for evaluating the environmental effects of chemical substances. Additionally, as an indispensable tool in genetics, cellular biology, and developmental research, this post considers how insights gained from plant systems may also inform mechanisms relevant to human health, further broadening the scope of New Approach Methodologies.
The Mustard Plant Model
The small flowering plant A. thaliana is a widely used biological model in modern biological research due to its experimental accessibility for various fields, including plant genetics, cell biology, and environmental development. As the first plant genome to be fully sequenced back in 2000, the simple, mappable genome and its short development period (6 weeks from germination to seed production in standard laboratory conditions) gave it initial favor for experimentation. On top of that, the mustard plant has high fecundity, with a single parent able to produce a large number of offspring seeds, and it is very small and easy to cultivate in controlled lab environments. In fact, in 2022, NASA reported the successful cultivation of Arabidopsis using lunar sediment, demonstrating its resilience and ease of use.
There are currently no alternative evaluation methods that involve A. thaliana as a New Approach Methodology, according to the EPA’s designated 2021 NAMs list. The most closely related NAM test guideline is OECD 221, which assesses the toxicity of substances absorbed into soil and aquatic environments using freshwater plants such as duckweed. In this test, the aquatic flowering cousin of the terrestrial weed Arabidopsis is exposed to various concentrations of a chemical over a few days, and researchers measure the effects of the substance on plant growth. In contrast, A. thaliana can provide a more experimentally accessible model for similar environmental impact and toxicity studies for the previously described reasons, and due to its well-characterized genome, researchers can examine underlying genetic and cellular mechanisms in such chemical stress responses.
The applications of using Arabidopsis as a model are diverse, ranging from basic scientific research to environmental toxicology, but a question remains: how can this model be consistently translated to human health for toxicity testing? Unlike zebrafish or mammals, plants do not share comparable organ systems with humans, and their developmental processes follow a fundamentally different biological framework. The real potential of Arabidopsis has always been seen in the multitude of core cellular processes shared across most eukaryotic organisms, such as vesicle trafficking and DNA repair, which are crucial to the cell cycle and the upkeep of the fundamental unit of life. Even comparing Arabidopsis to humans, these mechanisms are remarkably conserved, and Arabidopsis provides an efficient system for studying how environmental contaminants influence cellular stress responses and genetic regulation.
Overall, the opportunities for using Arabidopsis thaliana are extensive, thanks to its unique advantages and the surprising similarities between its cellular processes and those of humans. The current obstacles to its full implementation as a New Approach Methodology lie not in its experimental feasibility or reproducibility, but more in the standardization and regulatory acceptance of plant-based models for assessing human health endpoints. Should the scientific community seek to incorporate Arabidopsis thaliana more formally into a battery of tests for evaluating environmental toxicity, there would need to be increased effort to coordinate and standardize laboratory conditions across its use in toxicity studies.
Works Cited
https://www.epa.gov/assessing-and-managing-chemicals-under-tsca/strategic-plan-reduce-use-
https://www.science.org/doi/10.1126/science.282.5389.662
https://academic.oup.com/trends/plants/article/7/9/405/2588425
https://pmc.ncbi.nlm.nih.gov/articles/PMC11874203/
The views expressed do not necessarily reflect the official policy or position of Johns Hopkins University or Johns Hopkins Bloomberg School of Public Health.
