Q.An association between roots of higher plants and fungi is called
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Lichens and Mycorrhiza: Two Masterpieces of Symbiosis
Imagine two very different organisms deciding to live together — not as enemies, not as indifferent neighbours, but as partners who each bring something the other lacks. That is symbiosis, and lichens and mycorrhiza are two of the most elegant examples you will meet in biology.
Lichens: The Pioneer Painters
Walk past an old stone wall, a tree trunk, or a bare rock in a clean mountain region. That crusty, flaky, often colourful patch you see — grey, orange, greenish — is a lichen. It looks like a single plant, but it is not. A lichen is a partnership between a fungus (the mycobiont) and an alga (the phycobiont). Sometimes the alga is replaced by a cyanobacterium.
The fungus builds the structure — a protective, spongy body that holds water and minerals. The alga, tucked safely inside, does what algae do best: photosynthesis. It makes food (sugars) using sunlight, carbon dioxide, and water. The fungus cannot photosynthesise; it has no chlorophyll. So the alga feeds the fungus. In return, the fungus gives the alga a home, shelter from drying out, and a steady supply of mineral nutrients it absorbs from the rock or bark.
The lichen is not a single species. It is a dual organism — a stable, self-contained ecosystem in miniature.
Because lichens absorb everything from the air and rain — including pollutants — they are extremely sensitive to air quality. Sulphur dioxide, heavy metals, and acid rain kill them quickly. That is why they are used as bioindicators: a place rich in lichens has clean air. A place with no lichens likely has serious pollution.
In exams, remember: lichens = fungus + alga. The fungus provides structure and minerals; the alga provides food. Pollution kills the alga first, so the whole lichen dies.
Mycorrhiza: The Underground Network
Now go underground. Most plants — over 80% of all land plants — do not rely only on their own roots to absorb water and minerals. They team up with fungi in a partnership called mycorrhiza (literally "fungus-root").
The fungus grows into or around the plant's root cells, forming a dense network of threads (hyphae) that extend far beyond the root into the soil. These hyphae are incredibly thin — much thinner than root hairs — so they can reach into tiny soil pores where water and phosphate ions are trapped. The fungus absorbs these nutrients and passes them to the plant.
What does the fungus get in return? The plant is a photosynthetic machine. It sends sugars and organic compounds down to the roots, and the fungus takes its share. The plant feeds the fungus; the fungus feeds the plant.
| Feature | Lichen | Mycorrhiza |
|---------|--------|------------|
| Partners | Fungus + alga (or cyanobacterium) | Fungus + plant root |
| Who photosynthesises? | The alga | The plant |
| Who provides minerals? | The fungus (from rock/air) | The fungus (from soil) |
| Who provides food? | The alga | The plant |
| Where found? | On surfaces (rocks, bark, soil) | Underground, on/in roots |
| Key role | Pollution indicator, pioneer on bare rock | Nutrient absorption (especially phosphorus) |
A common mistake: thinking mycorrhiza is a disease or a parasite. It is not. Both partners benefit. The plant grows better with mycorrhiza than without it, especially in poor soil.
The Big Picture
Both lichens and mycorrhiza are mutualistic symbioses — both partners gain. But they solve different problems. …
Option (C) Mycorrhiza is correct.
- Mycorrhiza is the symbiotic association formed between fungi and the roots of higher plants.
- A lichen (A), by contrast, is a symbiotic association between algae and fungi, not between fungi and plant roots. …
The fungus-root partnership in higher plants is called mycorrhiza, option (C).
Fungi are capable of living as symbionts in two distinct partnerships: with algae, forming lichens, and with the roots of higher plants, forming mycorrhiza. In a mycorrhizal association the fungus benefits the plant by improving its ability to take up water and nutrients through the soil, while itself gaining organic nutrition from the plant. …
- TG EAPCET 2026Set ap-2026-05-04-AN1 markMCQQ.These seeds cannot germinate and establish without the presence of mycorrhizae are (A) Cycas (B) Gnetum (C) Ephedra (D) Pinus
›Reveal solutionSolution
The key idea is that certain gymnosperm seeds require a mycorrhizal association for germination and early establishment. Among the given options, Pinus seeds are known to depend on mycorrhizal fungi for successful germination and growth. The correct answer is (D) Pinus.
The question tests your understanding of a specific ecological relationship in gymnosperms: mycorrhizae. Mycorrhizae are symbiotic associations between fungi and plant roots. The fungus helps the plant absorb water and minerals (especially phosphorus) from the soil, while the plant provides the fungus with carbohydrates. For some plants, this relationship is not just beneficial but essential — without it, the seeds cannot germinate or the seedlings cannot survive.
Among the four options — Cycas, Gnetum, Ephedra, and Pinus — all are gymnosperms. But only one is famously dependent on mycorrhizae for its seeds to germinate and establish.
- Cycas is a cycad. Cycads often have coralloid roots that host nitrogen-fixing cyanobacteria, not mycorrhizae. Their seeds germinate without requiring mycorrhizal fungi.
- Gnetum is a gnetophyte. It can form mycorrhizae in some cases, but it is not obligately dependent on them for seed germination.
- Ephedra is also a gnetophyte. It grows in arid regions and can survive without mycorrhizae; its seeds do not require them. …
- TG EAPCET 2025Set ap-2025-04-29-FN1 markMCQQ.Which seeds cannot germinate and establish without the presence of mycorrhizae? (A) Gnetum (B) Ephedra (C) Cycas (D) Pinus
›Reveal solutionSolution
Orchid seeds are famously dependent on mycorrhizal fungi for germination, but among gymnosperms, Pinus (pine trees) have an obligate relationship with ectomycorrhizae that is essential for seedling establishment and survival in natural conditions.
Why Mycorrhizae Matter for Seed Germination
Mycorrhizae are symbiotic associations between fungi and plant roots. While many plants benefit from these partnerships, only certain species have evolved such complete dependence that their seeds cannot successfully germinate and establish without fungal partners. This typically occurs when:
- Seeds lack sufficient nutrient reserves
- Seedlings require specific nutrients (especially phosphorus and nitrogen) that are difficult to obtain from poor soils
- The plant has co-evolved with fungi to the point of obligate dependency
Analyzing Each Option
Let me work through each gymnosperm genus to identify which has this obligate requirement:
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Gnetum - This tropical/subtropical gymnosperm can form mycorrhizal associations, but these are facultative (optional). Gnetum seeds contain adequate endosperm and can germinate independently in suitable conditions.
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Ephedra - These desert-adapted gymnosperms are quite hardy and self-sufficient. While they may benefit from mycorrhizae in nutrient-poor environments, they don't require them for germination and establishment. Their seeds are adapted to harsh, often fungus-poor desert conditions.
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Cycas - Cycads do form mycorrhizal associations and benefit from them, but their large seeds contain substantial nutrient reserves. They can germinate and establish without mycorrhizae, though growth may be enhanced with fungal partners. …
- TG EAPCET 2025Set ap-2025-04-30-FN1 markMCQQ.Consider the following statements Assertion (A): Members of genus Glomus form mycorrhiza Reason (R): Fungal symbiont facilitates the absorption of manganese by the plant from the soil The correct answer is (A) Both (A) and (R) are true, (R) is the correct explanation of (A) (B) Both (A) and (R) are true, (R) is not the correct explanation of (A) (C) (A) is true, but (R) is false (D) (A) is false, but (R) is true
›Reveal solutionSolution
The assertion is true — Glomus species do form mycorrhiza — but the reason is false because the fungal symbiont primarily helps absorb phosphorus, not manganese. So (A) is true, (R) is false.
The question tests your knowledge of mycorrhizal associations — specifically, which nutrient the fungus helps the plant absorb. Many students remember that mycorrhiza improves mineral uptake but mix up the specific element. Let’s get the facts straight.
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Assertion (A): Members of genus Glomus form mycorrhiza.
Glomus is a well-known genus of arbuscular mycorrhizal fungi (AMF). These fungi form a mutualistic association with the roots of most terrestrial plants. The fungus colonises the root cortex and develops arbuscules (tree-like structures) inside cortical cells, where nutrient exchange happens. This statement is true.
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Reason (R): Fungal symbiont facilitates the absorption of manganese by the plant from the soil.
The primary benefit the plant receives from mycorrhizal fungi is enhanced uptake of phosphorus (as phosphate ions), which is often immobile in soil. The fungal hyphae extend far beyond the root depletion zone and deliver phosphorus to the plant in exchange for carbohydrates. While mycorrhiza can also improve the uptake of other micronutrients like zinc and copper, manganese is not the main one — and the statement specifically says "manganese", which is incorrect as a general role. Moreover, in some cases, mycorrhizal colonisation can even reduce manganese uptake by the plant. So this reason is false. …
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