What share of the total carbon accessed by plants can mycorrhizal fungi obtain?

1. Mycorrhizae are mutualistic, so the fungus must be paid for the minerals it delivers. 2. The payment is carbon, and the fungi can obtain up to 20 percent of the total carbon accessed by plants. 3. That is a large share, which is why the benefit to the plant is clearest in poor soils where minerals are hard to reach. 4. The fungus also acts as a physical barrier to pathogens and can induce generalised host defences. 5. Some mycorrhizal fungi additionally produce antibiotic compounds. 6. Values of 5 or 10 percent understate the cost of the partnership to the plant. _Source: OpenStax Biology (1st ed., CC BY 4.0), Ch 31 "Soil and Plant Nutrition", section 31.3 Nutritional Adaptations of Plants_