Role of Mycorrhizae in Plant Nutrition Nature’s Underground Partnership
Role of Mycorrhizae in Plant Nutrition Nature’s Underground Partnership - Beneath the soil, an extraordinary partnership thrives one that has shaped plant evolution for millions of years. This is the symbiotic relationship between plants and fungi, known as mycorrhizae.
The term mycorrhiza comes from Greek: mykes meaning “fungus” and rhiza meaning “root.” Together, they form a mutually beneficial association where both partners gain vital advantages. The role of mycorrhizae in plant nutrition is fundamental, influencing how plants absorb nutrients, resist stress, and sustain growth even in poor soils.
In this article, we’ll explore what mycorrhizae are, how they work, their types, and their importance in plant nutrition, soil health, and sustainable agriculture.
What Are Mycorrhizae?
Mycorrhizae are specialized associations between plant roots and beneficial fungi. In this relationship:
- The fungus colonizes the plant’s root system, extending far into the soil.
- The plant supplies carbohydrates (like glucose and sucrose) produced during photosynthesis to the fungus.
- The fungus, in return, helps the plant absorb nutrients and water from the soil more efficiently.
This symbiotic system creates an extended root network, known as the mycorrhizal network, sometimes referred to as the “wood wide web”, allowing plants to access nutrients beyond their normal reach.
Types of Mycorrhizae
There are two main types of mycorrhizal associations: ectomycorrhizae and endomycorrhizae (also called arbuscular mycorrhizae).
1. Ectomycorrhizae
- Form a sheath or mantle around the roots.
- Fungal hyphae (filaments) extend into the soil and between root cells but do not penetrate cell walls.
- Common in trees like pine, oak, birch, and eucalyptus.
- Enhance nitrogen and phosphorus uptake, particularly in forest ecosystems.
Example: The association between pines and Amanita fungi is a classic ectomycorrhizal relationship.
2. Endomycorrhizae (Arbuscular Mycorrhizae – AMF)
- The fungal hyphae penetrate the root cell walls but not the cell membranes.
- They form arbuscules (tree-like structures) inside root cells, increasing the surface area for nutrient exchange.
- Found in about 80–90% of all vascular plants, including most crops.
- Crucial for phosphorus, zinc, and copper absorption.
Example: Glomus species form AMF with many agricultural plants like maize, wheat, and legumes.
How Mycorrhizae Support Plant Nutrition
1. Enhanced Nutrient Uptake
One of the most vital roles of mycorrhizae is improving nutrient absorption. Fungal hyphae extend several centimeters beyond the root zone, accessing phosphorus (P), nitrogen (N), potassium (K), zinc (Zn), and copper (Cu) that roots alone cannot reach.
The fine network of fungal filaments increases the surface area for absorption by up to 100 times, making nutrient uptake faster and more efficient.
2. Improved Phosphorus Availability
Phosphorus is often locked in insoluble forms in the soil. Mycorrhizal fungi secrete organic acids and enzymes (like phosphatases) that dissolve phosphorus compounds, making them available for plant use.
This process is especially important in phosphorus-deficient or alkaline soils, where nutrient mobility is limited.
3. Enhanced Water Absorption
The fungal network acts as an extension of the root system, reaching moisture in distant soil pores. This improves drought tolerance by helping plants maintain hydration during dry periods.
Mycorrhizal plants often show better growth and yield under water stress compared to non-mycorrhizal plants.
4. Improved Soil Structure and Microbial Health
Mycorrhizal fungi secrete a glycoprotein called glomalin, which:
- Binds soil particles together, forming stable aggregates.
- Improves soil structure and aeration.
- Enhances water retention capacity.
- Promotes microbial diversity, creating a healthier rhizosphere ecosystem.
5. Increased Resistance to Pathogens and Environmental Stress
Mycorrhizae help plants resist root diseases caused by soil-borne pathogens like Fusarium and Pythium.
They achieve this by:
- Competing for space and nutrients in the rhizosphere.
- Inducing systemic resistance in plants (enhancing defense responses).
- Strengthening plant cell walls and metabolic activity.
Additionally, mycorrhizal plants are more resilient to heavy metal toxicity, salinity, and pH fluctuations.
6. Improved Nitrogen Fixation in Legumes
In leguminous plants, mycorrhizae work synergistically with Rhizobium bacteria, enhancing nitrogen fixation. The fungi improve phosphorus supply, which is crucial for nodule formation and nitrogenase enzyme activity.
As a result, legumes like soybean, pea, and lentil show improved nitrogen fixation and yield when inoculated with both mycorrhizae and rhizobia.
Mycorrhizae in Sustainable Agriculture
As farmers seek eco-friendly solutions to reduce chemical fertilizer use, mycorrhizal inoculants have become valuable tools in sustainable and organic farming.
Benefits include:
- Reduced dependence on chemical fertilizers.
- Improved soil fertility and nutrient recycling.
- Enhanced crop productivity under nutrient-poor or drought-prone conditions.
- Lower environmental pollution from fertilizer runoff.
Commercial biofertilizers containing mycorrhizal spores are now widely used in cereals, legumes, vegetables, and fruit crops.
The Ecological Role of Mycorrhizal Networks
Beyond individual plants, mycorrhizal fungi form interconnected underground networks linking multiple plants even between different species. Through this “common mycorrhizal network (CMN)”, plants can:
- Share nutrients and signaling molecules.
- Support seedlings by transferring carbon and minerals.
- Communicate warnings about pest attacks.
These networks help maintain forest stability and biodiversity, showing that mycorrhizae are essential not only for plant nutrition but for entire ecosystems.
Conclusion
The role of mycorrhizae in plant nutrition is vital and far-reaching. These beneficial fungi extend the plant’s root system, enhance nutrient and water uptake, improve soil health, and increase resistance to environmental stress.
In the face of modern challenges like soil degradation and climate change, understanding and utilizing mycorrhizal associations is key to sustainable agriculture and ecosystem resilience.
By nurturing these natural partnerships, we tap into one of the most powerful biological systems for building healthy, productive, and sustainable soils.