Protecting crops from radiation-contaminated soil

Almost four years after the accident at the Fukushima Daiichi Nuclear Power Plant in Japan, farmland remains contaminated with higher-than-natural levels of radiocesium in some regions of Japan, with cesium-134 and cesium-137 being the most troublesome because of the slow rate at which they decay.

In a study published in Scientific Reports, a group at the RIKEN Center for Sustainable Resource Science in Japan led by Ryoung Shin has identified a chemical compound that prevents plants from taking up cesium, thus protecting them—and us—from its harmful effects.

Although cesium has no beneficial function in plants, it is readily absorbed by plants in contaminated soil due to its water solubility and its similarity to potassium, a critical plant nutrient. After being absorbed, it continues to compete with potassium inside plant cells, disrupting physiological processes and causing major retardation in plant growth. Because of this, the research team focused their efforts on finding a way to prevent cesium uptake.

First, they used seedlings from the model plant Arabidopsis thaliana and tested 10,000 synthetic compounds to determine if any could reverse the harmful effects of cesium. The effects of each compound were quantified with a scoring scale, and after several screenings, they had found five compounds that made plants highly tolerant to cesium.

Next they looked at how these five compounds—termed CsTolen A-E—produced their effects. They found that when Arabidopsis was grown in cesium-containing liquid media with CsTolen A, more cesium remained in the liquid medium and much less was found in the plants. Importantly, the concentration of CsTolen A needed for this effect did not prevent the plants from absorbing the potassium that they need to grow.