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:
1, 2 and 3
Understanding Mycorrhizal Biotechnology for Degraded Site Rehabilitation
Mycorrhiza refers to the symbiotic relationship between fungi and plant roots. This partnership is incredibly beneficial for both organisms, especially the plant, particularly when growing in challenging environments like degraded sites. Mycorrhizal biotechnology leverages this natural association to help plants establish and thrive in poor soil conditions, aiding in ecological restoration.
Let's examine how mycorrhiza helps plants, considering the given statements:
Statement 1: Resist Drought and Increase Absorptive Area
This statement is accurate. Mycorrhizal fungi form a vast network of thin filaments called hyphae that extend far into the soil, beyond the reach of the plant's own roots. These hyphae are much finer than root hairs and can access water and nutrients in smaller pores or from further distances in the soil. This effectively increases the overall absorptive surface area for the plant. By accessing more water, mycorrhizal plants are often more resistant to drought stress, a common issue in degraded sites.
Statement 2: Tolerate Extremes of pH
This statement is also correct. Degraded sites often suffer from pH imbalance (either too acidic or too alkaline), which affects nutrient availability and can be toxic to plants. Mycorrhizal fungi can help plants tolerate these extreme pH conditions. They can modify the rhizosphere (the soil area around the roots) pH or help in immobilizing or chelating toxic ions (like heavy metals) that are more soluble and available at extreme pH values. This protects the plant from toxicity and allows it to absorb necessary nutrients.
Statement 3: Resist Disease Infestation
This statement is also valid. Mycorrhizal associations can enhance plant defense mechanisms against pathogens. The fungal hyphae can create a physical barrier around the root surface, preventing pathogens from infecting the root. Additionally, mycorrhizal colonization can induce systemic resistance in the plant, making it more resilient to diseases affecting other parts. Competition for resources in the rhizosphere by the mycorrhizal fungi can also suppress the growth of harmful soil-borne pathogens.
Conclusion on Mycorrhizal Benefits in Rehabilitation
Based on the analysis of each statement, all three benefits—increased drought resistance and absorptive area, tolerance to pH extremes, and resistance to disease—are well-documented advantages conferred by mycorrhizal associations to plants. These benefits are crucial for the successful establishment and growth of vegetation in degraded or harsh environments, making mycorrhizal biotechnology a valuable tool in rehabilitation efforts.
| Mycorrhizal Benefit | Explanation for Rehabilitation |
|---|---|
| Resist Drought / Increase Absorption | Fungal hyphae extend root reach for water and nutrients. |
| Tolerate pH Extremes | Modify rhizosphere, sequester toxic ions, improve nutrient uptake in poor soils. |
| Resist Disease | Physical barrier, induce plant defense, compete with pathogens. |
Revision Table: Key Benefits of Mycorrhiza in Rehabilitation
| Benefit | Mechanism | Relevance to Degraded Sites |
|---|---|---|
| Improved Water Uptake | Extensive hyphal network reaches beyond root depletion zone. | Crucial for drought-prone or low-water availability sites. |
| Enhanced Nutrient Acquisition (especially Phosphorus) | Hyphae efficiently explore soil and mobilize less available nutrients. | Important for nutrient-poor soils common in degraded areas. |
| Increased Tolerance to Environmental Stressors | Buffering pH, immobilizing toxic heavy metals, improving soil structure. | Addresses issues like soil acidity/alkalinity, heavy metal contamination. |
| Enhanced Plant Defense against Pathogens | Physical barrier, competition, induced systemic resistance. | Helps plants survive in challenging environments with potential pathogen load. |
Additional Information on Mycorrhiza and Rehabilitation
Mycorrhizal biotechnology involves introducing or enhancing the presence of beneficial mycorrhizal fungi in degraded soils to support plant growth. Different types of mycorrhiza exist, including:
- Arbuscular Mycorrhiza (AM): Found in most plant species (around 80%), including many crops and grasses. The fungi penetrate plant root cells, forming structures like arbuscules and vesicles.
- Ectomycorrhiza (ECM): Primarily associated with trees and shrubs (like pines, oaks, birches). The fungi form a sheath around the root tip and a network (Hartig net) between root cells but do not penetrate the cells themselves.
Selecting the appropriate type of mycorrhizal inoculum based on the plant species and the specific conditions of the degraded site is important for successful rehabilitation projects. Mycorrhiza not only helps individual plants but also contributes to improving soil structure and overall ecosystem health in degraded areas.
