The Rhizosphere: its importance in the Ecosystem

Background

The ground beneath Heene Cemetery is shared between the remains of the 1960 men women and children buried there between 1873 and 1977 and the soil which is full of plant roots.

The rhizosphere is a small area of soil surrounding plant roots. Even though it is very thin, it is full of life and chemical activity. Plants interact with soil organisms here, which helps them grow, fight diseases, and access nutrients. The rhizosphere is critical for the health of plants and the functioning of ecosystems (Philippot et al., 2013).

Plants Shape the Rhizosphere

Plants release sugars, amino acids and other compounds. These are called exudates. Exudates feed microorganisms and attract specific types of bacteria and fungi to the root area (Bais et al., 2006). Different plants produce different exudates, which helps create unique microbial communities around their roots (Dakora & Phillips, 2002).

Microbes in the Rhizosphere

The rhizosphere is rich in microorganisms like bacteria, fungi, archaea, and protozoa. Among them, bacteria and fungi are the most common. Some bacteria, called plant growth-promoting rhizobacteria (PGPR), help plants by fixing nitrogen, producing plant hormones, and protecting roots against harmful microbes (Lugtenberg & Kamilova, 2009). Fungi, especially mycorrhizal fungi, form partnerships with roots and help plants absorb nutrients like phosphorus in exchange for sugars (Smith & Read, 2008). Most conifers, ferns, mosses and flowering plants are dependent on mycorrhizal fungi. The common spotted orchid would not be able to develop without mycorrhiza as it does not have an initial food supply.

Microbes interact with Plants

Plants and microbes often work together. For example, rhizobia bacteria form nodules on legume roots to fix nitrogen, and mycorrhizal fungi help plants collect nutrients. However, not all interactions are positive. Some microbes cause root diseases. A healthy rhizosphere microbiome usually keeps harmful pathogens under control by outcompeting them and boosting the plant’s immune system (Berendsen et al., 2012).

The importance of the Rhizosphere

The rhizosphere is crucial for nutrient cycling, soil health, and sustainable agriculture. Understanding how it works can help farmers grow crops with fewer chemical inputs by using biofertilizers or managing soil to favor helpful microbes (Mendes et al., 2013). Microorganisms in the rhizosphere also play a role in storing carbon in soils, which could help fight climate change (Singh et al., 2010).

Summary

The rhizosphere is a small but vital zone around plant roots where plants and microbes interact. Through releasing exudates and partnering with microbes, plants can grow better, access nutrients, and defend themselves against diseases. Some plants, such as the common spotted orchid, would not be able to develop with the rhizosphere.

References

Bais, H. P., Weir, T. L., Perry, L. G., Gilroy, S., & Vivanco, J. M. (2006). Annual Review of Plant Biology, 57, 233–266. Berendsen, R. L., Pieterse, C. M. J., & Bakker, P. A. H. M. (2012). Trends in Plant Science, 17(8), 478–486. Dakora, F. D., & Phillips, D. A. (2002). Plant and Soil, 245(1), 35–47. Lugtenberg, B., & Kamilova, F. (2009). Annual Review of Microbiology, 63, 541–556. Mendes, R., Garbeva, P., & Raaijmakers, J. M. (2013). FEMS Microbiology Reviews, 37(5), 634–663. Philippot, L., Raaijmakers, J. M., Lemanceau, P., & van der Putten, W. H. (2013). Nature Reviews Microbiology, 11(11), 789–799. Singh, B. K., Bardgett, R. D., Smith, P., & Reay, D. S. (2010). Nature Reviews Microbiology, 8(11), 779–790. Smith, S. E., & Read, D. J. (2008). Mycorrhizal Symbiosis (3rd ed.). Academic Press.

By John Brownbill and a friend.