Root Economics - Between Do-It-Yourself Strategies and Fungal Outsourcing

Root economics  Image Credit: © Authors of the study

Root economics Image Credit: © Authors of the study

International group of researchers with members from Freie Universität Berlin describes the growth strategies of plant roots.

No 115/2020 from Jul 02, 2020

An international group of researchers with members from Freie Universität Berlin, the German Center for Integrative Biodiversity Research (iDiv), and Wageningen University, among others, has been studying the complex belowground economy of roots. Under the direction of Dr. Joana Bergmann (Freie Universität Berlin), the biologists describe in their study the different growth strategies found in root systems and how they "collaborate" with fungi. Their findings are based on the analysis of approximately 1,800 plant species from around the world and the specific traits of their roots. The research group found that the formation of the root growth often depends on symbiosis with fungi. This insight will help scientists better understand "root economics" and the adaptations and exchanges that take place belowground as well as how environmental changes affect these relationships. The study was published in the prestigious journal Science Advances.

Through photosynthesis, plants have the ability to convert light into chemical energy and to bind carbon, the basic biochemical building block. They absorb vital substances from the soil through their roots - nutrients, minerals, and water. The authors of the study compare these metabolic processes with economic value chains. In plant economies, carbon is the main currency. Plants can invest carbon to promote organ growth, for example, to produce leaves, flowers, seeds, or roots.

It has long been known that plants follow different growth strategies when forming their aboveground organs, especially leaves. Short-lived leaves, for example, can be produced in a relatively cost-efficient way, but can only photosynthesize and bind carbon for a limited time. Long-lived leaves, on the other hand, demand higher investments, but continue to function for a longer period. Dr. Joana Bergmann’s research team was able to prove that root growth, too, follows similar economic principles. How roots develop and how long they live depend on a plant’s biochemical investments in carbon and energy.

However, according to the study, symbiosis with mycorrhizal fungi has an especially strong influence on root traits. Many plants "outsource" their nutrients supply chain below ground to varying degrees. Fungi provide them with soil nutrients through special exchange methods. The fungi are then paid in carbon through the plant roots. The scientists discovered that the adaptations that enable the symbiotic exchange with fungi have a significant effect on root traits. In addition, closely related plants tend to show similar patterns in how their roots grow.

This give-and-take relationship has adapted along evolutionary lines over time, explains Joana Bergmann, lead author of the research project. The "division of labor" between plants and fungi, she says, depends on the plant phylogeny. Plants have many different growth strategies and collaborative methods - such as fungal outsourcing - that they can use to acquire the nutrients they need.

The paper is a joint effort of the working group sROOT. sDiv, the synthesis center of the German Center for Integrative Biodiversity Research (iDiv), finances working group meetings with 10 to 20 international scientists to work on current scientific issues, funded by the German Research Foundation (FZT 118).

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