Question

Which of the following microorganism can undertake symbiotic relationship with plants?

• A. Virus
• B. Fungi
• C. Mycoplasma
• D. Protozoa

Hint:

Mycorrhiza (literally "fungus-root") is the most common mutualistic symbiosis in the plant kingdom, present in over $80\%$ of land plants. It is highly critical for phosphorus nutrition in agriculture.

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Symbiosis is a close, long-term biological interaction between two different organisms.
Many terrestrial plants establish highly specialized mutualistic relationships with soil microorganisms to enhance their nutrient uptake and stress tolerance.

Step 2: Detailed Explanation:
Among the listed microorganisms, Fungi are highly renowned for establishing widespread and essential symbiotic relationships with plants, known as Mycorrhizae.
There are two main types of mycorrhizal associations:
1. Arbuscular Mycorrhizae (AM): Glomeromycete fungi penetrate the cortical cells of plant roots, forming highly branched structures called arbuscules where nutrient exchange occurs.
2. Ectomycorrhizae: Fungal hyphae cover the root surface as a mantle and grow between cortical cells (Hartig net) without penetrating them, common in temperate trees.
In these associations:
- The plant provides the fungus with photosynthetically fixed carbon (sugars).
- The fungal hyphal network extends far into the soil, greatly increasing the root's effective surface area to absorb water and immobile nutrients, particularly phosphorus.
Other listed entities like viruses and mycoplasmas are strictly pathogenic and do not form mutualistic symbioses with plants.

Step 3: Final Answer:
Fungi establish mutualistic symbiotic relationships with plants, corresponding to option (B).