Study reveals how plant roots penetrate hard soil

In a new study from the University of Nottingham, researchers have designed plant roots that are capable of penetrating hard soil. The study, which was focused on cereal plants, is a promising new step toward “climate-proofing” vital crops as global warming leads to less rainfall and drier soils.

“Soil compaction represents a major agronomic challenge, inhibiting root elongation and impacting crop yields,” wrote the study authors. 

“Roots use ethylene to sense soil compaction as the restricted air space causes this gaseous signal to accumulate around root tips. Ethylene inhibits root elongation and promotes radial expansion in compacted soil, but its mechanistic basis remains unclear.” 

The researchers identified the genes, hormone signals and processes that control the ability of rice roots to penetrate hard soils.

“Here, we report that ethylene promotes abscisic acid (ABA) biosynthesis and cortical cell radial expansion. Rice mutants of ABA biosynthetic genes had attenuated cortical cell radial expansion in compacted soil, leading to better penetration.”

When crops encounter hard soils, their roots tend to grow shorter and swell – which was thought to help penetrate hard soils. In the new study, however, X-ray imaging revealed that narrow roots can better penetrate hard soils.

When the experts reduced the level of the hormone that promotes root swelling, the plant roots remained narrow and maintained their ability to penetrate hard soil.

“Our research overturns decades of scientific thinking, revealing that root swelling does not help penetrate hard soils. These results can potentially safeguard or boost agricultural yields worldwide, particularly considering that climate change can exacerbate the strength of soil by less rainfall,” said Dr. Bipin Pandey, the study’s lead researcher. “This new understanding of how roots grow in hard soils promises to help develop novel soil-compaction-resistant crops.”

The study is published in the journal Proceedings of the National Academy of Sciences.

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By Chrissy Sexton, Earth.com Staff Writer