Final answer:
In mycorrhization, a plant primarily obtains phosphorus, which is crucial for root development and the creation of seeds and fruits. Mycorrhizal fungi in turn benefit from the carbohydrates provided by the plant and help the plant by increasing its nutrient absorption surface area.
Step-by-step explanation:
Mycorrhization and Plant Nutrient Uptake
Through the symbiotic process of mycorrhization, the mutual benefits between fungi and the roots of a plant allow for an efficient uptake of nutrients from the soil. One of the most important nutrients that a plant obtains through this relationship is phosphorus, which is essential for the development of roots, flowers, seeds, and fruits. Other minerals that may be provided by mycorrhizal fungi include zinc and copper. In this symbiotic partnership, the fungus benefits by obtaining carbohydrates, such as sugars, from the plant. Furthermore, mycorrhizal networks can enhance the plant's ability to access nutrients by increasing the surface area for absorption, reaching into soil realms otherwise inaccessible, and sometimes producing antibiotic compounds that ward off pathogens.
In comparison to rhizobia, mycorrhizal fungi do not facilitate nitrogen fixation but instead focus on the mobilization of phosphorus, among other nutrients. Despite the importance of potassium in the context of rhizobia and nitrogen fixation, it is phosphorus that is the primary nutrient involved in mycorrhization. Therefore, the correct answer to the question is b) Phosphorus.