UPSC Prelims 2013 Q97: Environment & Ecology – Sustainable Agriculture & Forestry
Mycorrhizal biotechnology has been used in rehabilitating degraded sites because
mycorrhiza enables the plants to
1. Resist drought and increase absorptive area
2. Tolerate extremes of pH
3. Resist disease infestation
Select the correct answer using the codes given below:
- (a) 1 only
- (b) 2 and 3 only
- (c) 1 and 3 only
- (d) 1, 2 and 3
Answer: (d) 1, 2 and 3
Explanation
Mycorrhiza in rehabilitating degraded sites
Mycorrhiza is a symbiotic association between a fungus and the roots of a plant.
The fungus gets sugars; the plant gets water and nutrients.
| Benefit to the plant | True? | How |
|---|---|---|
| 1. Resist drought and increase absorptive area | Yes | Fungal threads (hyphae) spread far beyond the roots |
| 2. Tolerate extremes of pH | Yes | Helps plants survive in acidic or alkaline soils |
| 3. Resist disease infestation | Yes | Protects roots from root-borne pathogens |
Other benefits:
| Benefit | Detail |
|---|---|
| Phosphorus uptake | The best-known role; the fungus unlocks soil phosphorus |
| Heavy metals | Helps plants tolerate mine waste |
| Example | The fungus Glomus is widely used |
So mycorrhiza is used to re-green mine dumps and wastelands.
Answer: (d) 1, 2 and 3.
Why each option is right or wrong
- (a) Incorrect. It also helps plants tolerate extreme pH and resist disease.
- (b) Incorrect. It also helps plants resist drought.
- (c) Incorrect. It also helps plants tolerate extremes of pH.
- (d) CORRECT. Mycorrhiza helps with drought, pH extremes and disease.
Key point
Mycorrhiza: fungus-root symbiosis; more absorptive area, phosphorus uptake, drought and pH tolerance, disease resistance; used to reclaim mine waste.
Remember
Mycorrhiza = fungus on roots, better survival.
Common mistakes
- Confusing mycorrhiza (fungus + root) with lichen (fungus + alga).
- Thinking it fixes nitrogen; its main gift is phosphorus.
- Forgetting that the fungus also gains sugars.
Exam tip
Myco = fungus, rhiza = root. A helpful fungus widens the root's reach.
Sources
- NCERT Class XII — Biology (Microbes in Human Welfare: microbes as biofertilisers)
- The Energy and Resources Institute — Mycorrhiza for reclamation of degraded land