Lawns are sometimes fertilized with nitrate that can be washed into neighboring woodlots by rain. If the trees in that woodlot are associated with EMF, what effect might the excess nitrate have on the fungi and/or trees? a. Fungal growth may be stimulated, causing the trees to transport more nitrogen to the fungi. b. The fungi may secrete more peptidases to break down the nitrate. c. The trees may take up the nitrate directly into their roots and rely less on the fungi. d. The excess nitrate may stimulate the fungi to transport more sugar to the trees.

Verified step by step guidance

1. Understand the relationship between trees and ectomycorrhizal fungi (EMF). EMF forms a symbiotic relationship with trees, where fungi help the trees absorb nutrients like nitrogen from the soil, and in return, trees provide the fungi with carbohydrates (sugars).
2. Consider the role of nitrate as a nitrogen source. Nitrate is a form of nitrogen that plants, including trees, can directly absorb through their roots from the soil.
3. Analyze the impact of excess nitrate. If nitrate levels increase due to fertilization, trees might not rely as heavily on EMF for nitrogen since they can absorb it directly from the soil.
4. Evaluate the options given in the problem. Option c suggests that trees may take up the nitrate directly into their roots and rely less on the fungi, which aligns with the understanding that trees can absorb nitrate directly when available in excess.
5. Conclude that the most likely effect of excess nitrate on the relationship between trees and EMF is that trees will rely less on the fungi for nitrogen absorption, as stated in option c.

Key Concepts

Ectomycorrhizal Fungi (EMF)

Ectomycorrhizal fungi form symbiotic relationships with the roots of many trees, enhancing nutrient uptake, particularly nitrogen and phosphorus. In this association, the fungi extend their hyphae into the soil, increasing the surface area for absorption. The trees, in return, provide carbohydrates to the fungi, creating a mutualistic relationship that is crucial for the health of both organisms.

Nitrate Assimilation

Nitrate assimilation is the process by which plants and fungi convert nitrate, a form of nitrogen, into organic compounds. This process is vital for growth, as nitrogen is a key component of amino acids and nucleic acids. In the context of excess nitrate from fertilizers, both trees and fungi may alter their nutrient uptake strategies, potentially affecting their symbiotic relationship.

Nutrient Competition

Nutrient competition refers to the struggle between plants and fungi for available nutrients in the soil. When excess nitrate is introduced, it can shift the balance of this competition, potentially leading trees to rely less on their fungal partners for nitrogen. This shift can impact the dynamics of the ecosystem, influencing both fungal growth and tree health.