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Plant roots grow toward soil fungi

02 December 2020

Wageningen

Roots of plants not only release odors themselves, but also appear to react to odors that are secreted by beneficial and harmful fungi in the soil.

They do this by growing towards the fungi, or ignoring them. This 'sense of smell' has a positive influence on the ultimate health of a plant. Exposure to the right fungi can sometimes even result in protection against insects and worms that feed on plants and their roots. This is evident from Kay Moisan's thesis that she will defend on October 16, 2020.

Plant roots are fascinating organs because they are so essential to plant health. However, we do not yet know how they function in the soil and which factors influence their growth. Recent studies show that roots can perceive the smells of microbes in the soil, and that smells of soil bacteria or soil fungi, for example, can influence the branching and length of plant roots.

Growth direction

However, until now it was unknown whether microbial fragrances can also influence the direction in which plant roots grow. In her dissertation and the accompanying publication in Plant, Cell and Environment , Kay Moisan and her co-authors from the Netherlands Institute for Ecology (NIOO-KNAW) and Wageningen University & Research demonstrate that this is the case. Plants perceive smells that produce soil fungi and react to them before they come into contact with the fungi.

To demonstrate this, scientists developed a unique test set-up in which rapeseed roots ( Brassica rapa ) in the soil were "given the choice" to grow in the direction of or away from the smells of four different soil fungi. For example, the researchers showed that roots ignore the odors that are secreted by certain fungi, but can also be attracted by the odors of other fungi. Interestingly, the plant roots are mainly attracted to odors that emit harmful fungi.

Opportunities for crop protection and stimulation


Exposure of plant roots to fungal odors can make plants less suitable as a food source for leaf-eating caterpillars, nematodes and root-eating insects.

In the quest for sustainable agricultural practices, soil microbial scents are therefore promising candidates for crop protection and stimulation. The findings also raise new follow-up questions about whether plants can actively "decide" where to grow and with which microorganisms to interact.

New research method

The design of the research is also a proof of concept that roots do react to microbial odors. “With the research, a new method has been realized to study the chemical communication between roots and soil fungi and its influence on root growth, and this setup can also be reused by other laboratories to further investigate these interactions,” said Moisan's promoter Prof. Marcel Dicke.

 

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