Q. Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to: - resist drought and increase absorptive area
- tolerate extremes of pH
- resist disease infestation
Select the correct answer using the codes given below. (UPSC Prelims 2013)
Answer:
1, 2 and 3
Notes: The correct answer is
[D] 1, 2 and 3. Mycorrhiza is a symbiotic association between a fungus and the roots of a vascular plant. This relationship is highly beneficial for land reclamation and the rehabilitation of degraded ecosystems because it enhances the plant's survival and growth under stress.
- Resist drought and increase absorptive area (Statement 1 is Correct): The fungal hyphae (thin, thread-like structures) extend far beyond the root system into the soil, significantly increasing the surface area available for the absorption of water and nutrients, especially phosphorus. This expanded network allows plants to access moisture from deeper or smaller soil pores that roots cannot reach, thereby increasing drought resistance.
- Tolerate extremes of pH (Statement 2 is Correct): Degraded sites, such as mine spoils or industrially contaminated lands, often have highly acidic or alkaline soils. Mycorrhizal fungi can modify the rhizosphere (the soil area surrounding the roots) by secreting organic acids and buffering the environment, which helps the host plant tolerate extreme pH levels and reduces the toxicity of heavy metals.
- Resist disease infestation (Statement 3 is Correct): Mycorrhizae provide a physical and chemical barrier against soil-borne pathogens. By occupying the root space and utilizing the root exudates, they outcompete harmful fungi and bacteria. Some mycorrhizal fungi also induce the plant's own defense mechanisms, making it more resilient to infections.
Role in Rehabilitation: In degraded sites, the soil is often "dead" or nutrient-depleted. Introducing mycorrhizal biotechnology helps rebuild the soil structure and nutrient cycling, acting as a "biological bridge" that allows pioneer plant species to establish themselves in hostile environments.