**5. Plant-microbe interactions and phosphorus-availability in the rhizosphere**

One of the most well-known plant-microbe interactions is the mycorrhizal association between plants and fungi (**Figure 5**). Mycorrhizal fungi form a symbiotic relationship with plant roots, where the fungi colonize the roots and extend their hyphae into the soil, increasing the surface area for nutrient uptake. In return, the fungi receive carbohydrates from the plant. Mycorrhizal fungi are particularly effective at accessing and mobilizing P in the soil, often found in low concentrations and insoluble forms. The fungi can release enzymes that break down organic forms of P and make them available for plant uptake [5].

Another type of microbes that can impact P availability in the rhizosphere are PSB. These bacteria convert insoluble forms of P into soluble forms, which plants can take up. PSB can release organic acids, chelating agents, and enzymes that solubilize P, making it available to the plant [97]. In addition to solubilizing P, PSB can enhance root growth and plant biomass by producing phytohormones [98].

#### **Figure 5.**

*Schematic representation of the major impacts of mycorrhizal assoctiations on phosphorus uptake on plant.*

Plant-microbe interactions in the rhizosphere can also affect the distribution of P in the soil. For example, some plant species can exude organic compounds that attract specific microbes, influencing the spatial distribution of P in the soil [99]. The presence of microbes in the rhizosphere can also alter the chemical properties of the soil, making it more favorable for plant growth and P uptake [100]. Research has also shown that PSB can interact synergistically with other soil microorganisms, such as mycorrhizal fungi, to further enhance plant growth and nutrient uptake. By promoting a diverse and healthy microbial community in the rhizosphere, PSB can help to create a more resilient and sustainable agricultural system.
