Question

Mycorrhizal fungi are commonly found attached to plant roots. The fungi are more efficient than plants at extracting nutrients from the soil. In exchange for nutrients, plants provide the fungi with sugars made through photosynthesis. However, when nutrients in the soil are abundant, researchers have found that plant growth increases if mycorrhizal fungi are removed. This phenomenon suggests that ____________.

Answer 1

When nutrients are abundant in the soil, plant growth can increase if mycorrhizal fungi are removed because plants can rely on their own roots for nutrient absorption, making the fungal relationship less beneficial.

Step-by-step explanation:

The phenomenon where plant growth increases when mycorrhizal fungi are removed in nutrient-rich soils suggests that plants do not always require the fungi for nutrient uptake and may instead rely on their own root systems when nutrients are readily available. This implies that the symbiotic relationship between plants and fungi may become less beneficial to the plant under certain conditions.

This mutualistic association, while typically advantageous for both plants and fungi, is context-dependent. Plants can provide fungi with sugars made through photosynthesis, and in return, the fungi use their hyphae to increase the surface area of roots, enhancing the plant's ability to absorb water and minerals from the soil, especially phosphorus. However, in scenarios where the soil is nutrient-rich, the cost of supplying the fungi with sugars outweighs the benefits of fungal-assisted nutrient uptake, leading to better growth when mycorrhizae are not present.