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Confocal image of radial cross sections of rice primary roots grown in 1.1 bulk density non-compacted soil.

Plants use chemical cues to avoid sending their roots (rice plant root pictured) into compacted soil. Credit: B.K. Pandey et al./Science

Plant sciences

The chemical flare that warns plants of rough going ahead

Elevated levels of a plant hormone tip off roots about compacted soil.

A plant hormone that helps fruit to ripen also stops roots from growing into hard, unwelcoming soil.

Healthy soil is soft and fluffy, but modern agricultural practices compact soil, making it hard and dense. Compacted soils limit plants’ access to water and nutrients, and can cause yields to drop.

Conventional wisdom suggested that hard soil physically blocks root growth, but Malcolm Bennett at the University of Nottingham, UK, Dabing Zhang at Shanghai Jiao Tong University in China and their colleagues tested a different hypothesis. They exposed healthy roots of rice plants (Oryza sativa) to ethylene, a plant hormone made by root tissue. In response, the roots stopped growing longer and started growing wider, as do roots growing in compacted soil. By contrast, compacted soil had almost no effect on the roots of mutant rice plants that were insensitive to ethylene.

The researchers also found that compacted soil slows the diffusion of ethylene from root tissue and allows it to accumulate in and around a root. They suggest that the hormone could warn roots against venturing into hostile ground.

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Pulsar wind nebula illustration

Curving purple lines in this artist’s impression represent the magnetic field of a neutron star (white sphere) left over from a brilliant supernova. Credit: Salvatore Orlando/INAF-Osservatorio Astronomico di Palermo

Astronomy and astrophysics

X-rays expose a clue to the mystery of the missing neutron star

Astronomers might have spotted the long-sought debris of a famous stellar explosion.
A bone fragment next to a dime

A bone fragment excavated in Southeast Alaska belonged to one of the earliest known domestic dogs in the Americas. Credit: Douglas Levere/University at Buffalo

Genomics

An ancient Alaskan dog’s DNA hints at an epic shared journey

To scientists’ surprise, a 10,000-year-old bone found in an Alaskan cave belonged to a domestic dog — one of the earliest known from the Americas.
Emissions billow from smokestacks at a coal-fired power plant as the sun sets, India.

Black carbon emitted by power plants and other sources in Asia wafts to the Arctic, where the pollution accelerates the melting of ice and snow. Credit: Kuni Takahashi/Bloomberg/Getty

Atmospheric science

Soot from Asia travels express on a highway to the high Arctic

Black carbon from fuel combustion in South Asia bolsters the effects of climate change on northern ice and snow.
Prevotella copri bacteria, computer illustration

The gut bacterium Prevotella copri (artist’s impression) has been linked to a reduction in the health benefits of a diet that skimps on red meat in favour of fish and vegetables. Credit: Kateryna Kon/Science Photo Library

Microbiology

Trying a Mediterranean diet? Gut microbes might sway the outcome

The composition of a person’s microbiome could influence the health effects of swapping steak for vegetables and olive oil.
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