Scientists discover plant roots possess "sense of smell" to avoid decay
Chinese scientists have identified a new behavior in plant roots, termed "saprotropism," enabling them to detect and steer clear of decomposing organic matter in the soil.
A research team led by Professor Zhang Yuzhou at Northwest A&F University has identified and defined a novel root behavior, termed "saprotropism," which allows plants to actively perceive and avoid areas of soil enriched with pathogens from decomposing plant tissues. This finding, published in the journal Science, addresses a long-standing scientific question about how stationary plants respond to soil-based threats.
Decomposition in ecosystems is crucial for nutrient cycling, but decaying matter also harbors microbes that can harm living plants. While animals can physically move away from hazards, plants' mechanisms for dealing with such proximity were unclear. The research demonstrated that when plant roots encounter decaying organic material, their growth is rapidly inhibited. This aversion response was observed across various plant species, including Arabidopsis, rapeseed, tomato, and wheat, suggesting it is a widespread survival strategy.
The study revealed that the "sense of smell" is triggered by acidic metabolites, such as organic and phenolic acids, released by fungi decomposing plant matter. These compounds create a localized acidic microenvironment in the soil, acting as a directional signal. The plant roots detect this acidity via a specific receptor module on their epidermal cells. This signal is then translated into an asymmetrical distribution of abscisic acid (ABA), a plant hormone, which reorients root growth away from the decay source. Notably, this mechanism operates independently of established auxin-based growth regulation pathways.
An intriguing aspect of the discovery is the specificity of the response: roots exhibit saprotropism only towards decaying plant material, not towards decaying animal matter. This suggests that animal decomposition products may not pose a threat to plant roots. The findings could lead to advancements in precision agriculture, such as optimizing straw incorporation into fields and developing crop varieties with enhanced resistance to root damage from improperly composted organic matter.