The plant root system is a complex and dynamic ecosystem that houses a variety of microorganisms, including bacteria, fungi, archaea, and protists, etc. These microorganisms together form the root microbiota. The root microbiota has a profound impact on plant growth and development, health, and adaptability to the environment. So, do the plants also have effects on the root microbiota? If so, how do the two interact with each other?
Researcher Yang Bai from Peking University and his research team have deeply explored this issue. The results recently published in the journal Frontiers of Agricultural Science and Engineering (DOI: 10.15302/J-FASE-2024595).
The study found that the soil nutrient status significantly affects the composition of the root microbiota. For example, long-term application of nitrogen fertilizers will change the structure of the soil microbial community. Due to the abundant nitrogen source, the number of nitrogen-fixing microorganisms decreases, while the nitrifying and denitrifying bacteria that prefer to utilize the existing nitrogen source increase significantly.
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Increasing the application of phosphorus fertilizers can stimulate the massive reproduction of phosphorus-solubilizing bacteria and mycorrhizal fungi. These microorganisms can convert the phosphorus in the soil, which is difficult for plants to absorb, into a utilizable form, thus significantly improving the plant’s phosphorus absorption efficiency.
Regulating the root microbiota
In addition, the nutrient-related genes of plants are also involved in regulating the root microbiota. When plants face nutrient stress, specific genes are activated, thereby changing the composition and quantity of root exudates. Taking phosphorus starvation as an example, after the relevant genes in plants are activated, the roots are prompted to secrete more organic acids. These organic acids can not only acidify the soil and dissolve insoluble phosphorus, but also act as signaling molecules to attract phosphorus-solubilizing microorganisms to gather around the roots, forming a mutualistic symbiotic relationship and helping plants obtain more phosphorus.
On the other hand, the root microbiota can effectively improve the availability of plant nutrients. Nitrogen-fixing microorganisms can convert nitrogen gas in the air into ammonia that plants can directly utilize, thus reducing the dependence on chemical nitrogen fertilizers in the agricultural production process. Phosphorus-solubilizing microorganisms release the fixed phosphorus in the soil for plant absorption by secreting phosphatases and organic acids. At the same time, a variety of plant hormones produced by microorganisms can regulate the growth and development of plant roots, making the roots more developed and further enhancing the plant’s nutrient absorption efficiency.
This study shows that there is a complex and close interaction between plants and the root microbiota in nutrient utilization. Environmental nutrient conditions and plant nutrient-related genes jointly regulate the composition and assembly of the root microbiota, while the root microbiota significantly affects the plant’s nutrient utilization efficiency by improving nutrient availability and regulating plant hormones.
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