Plant roots sense compacted soil through gaseous hormone signals

The volatile plant hormone ethylene allows plant roots to sense and avoid compacted soils, researchers report. Rendering roots insensitive to ethylene allowed them to penetrate compacted soils more effectively, the same group showed. The findings reveal how plants regulate their growth in response to soil compaction – a growing challenge facing modern agriculture worldwide – and could serve as a pathway for how breeders might select or develop new crops resilient to soil compaction. Driven in part by a growing reliance on heavy machinery and poor soil management practices, soil compaction can lead to declining crop yields by restricting root growth and limiting the availability and transport of water and nutrients. It’s been intuitively assumed that many plants’ roots often fail to grow in compacted soil simply because they cannot penetrate harder soils, leading to a cessation of growth. According to Binpin Pandey and colleagues, however, reduced root growth is not due to a physical inability to grow through compacted soil. Instead, the authors demonstrate how root growth is actively stymied by a build-up of ethylene – a gaseous plant hormone produced by root tissues. Pandey et al. evaluated the role of ethylene on rice plant root growth and found that mutant roots insensitive to ethylene were able to penetrate compacted soils more effectively than wildtype roots. The results suggest that ethylene will diffuse through loose and aerated soil – but not compacted soil, which hinders gas diffusion and causes the hormone to accumulate in root tissues until it triggers hormone responses that restrict growth.

For reporters interested in trends, a December 2020 study in Science by Ciro Cabal et al. addressed how one type of plant’s root growth responds to root growth of nearby plants. https://science.sciencemag.org/content/370/6521/1197

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