Problem 5 - Biology: The Unity and Diversity of Life

Question

The nutrition of some plants is enhanced by a mutually beneficial association between a root and a fungus. The association is known as a ________. a. root nodule b. mycorrhiza c. root hair d. hypha

Step-by-Step Solution

Answer

The answer is (b) mycorrhiza.

Step 1: Understand Key Terms

First, identify the key terms in the question. The term 'mutually beneficial association between a root and a fungus' suggests a symbiotic relationship where both the plant and the fungus benefit. This is a critical detail for solving the question.

Step 2: Define Each Option

Define what each answer choice represents. - Root nodule: A structure usually formed by nitrogen-fixing bacteria in legumes' roots. - Mycorrhiza: A symbiotic association between a plant root and a fungus. - Root hair: Small hair-like extensions of a root, increasing surface area for absorption. - Hypha: Basic structural unit of a fungus, not representing a mutual association as described.

Step 3: Match Definitions to the Question

The question asks for an association known as a specific term among the given options. Since a mycorrhiza is a mutual association between a plant root and a fungus, it matches the description provided in the question.

Step 4: Select the Correct Answer

From evaluating the options and definitions, the correct choice is (b) mycorrhiza, which correctly describes the mutualistic relationship between plant roots and fungi enhancing plant nutrition.

Key Concepts

Symbiotic Relationship

A symbiotic relationship is a close and often long-term interaction between two different biological species. In the case of plants and fungi, this interaction is mutually beneficial. This means that both the plant and the fungus gain advantages from each other's presence. The plant typically provides the fungus with organic compounds such as carbohydrates. These are essential for its growth and energy needs.
The fungus, in return, aids the plant by enhancing its nutrient absorption capacity, particularly for minerals like phosphorus, which might be limited in the soil. This synergy between plant and fungus is a fantastic example of nature working together for greater resilience and efficiency.

• Mutualism: Both organisms benefit.
• Improved nutrient uptake by plants.
• Energy supply to fungi through plant metabolites.

This form of relationship not only supports plant vitality but also contributes to healthy ecosystems by promoting nutrient cycling and soil structure stability.

Plant-Fungal Association

The connection between plant roots and fungi is known as a plant-fungal association. These commonly occur in most terrestrial ecosystems.
In this association, mycorrhiza is a primary form, acting as a bridge for nutrient exchange between the soil and plant roots. This tight association is due to the fungi's extensive network of hyphae, which extend far beyond the plant's root surface, accessing nutrients that would otherwise be out of reach for the plant.
Mycorrhizal networks not only help individual plants but also connect multiple plants together. This leads to resource sharing within a community.

• Extension beyond root surface via fungal hyphae.
• Nutrient uptake facilitation.
• Plants connected through shared mycorrhizal networks.

Such associations have existed for hundreds of millions of years, highlighting their crucial role in the evolution and development of plant life on Earth.

Plant Nutrition

Plant nutrition is a critical process for growth and survival, mainly achieved through the uptake of nutrients from the soil. Essential nutrients typically include nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
Mycorrhizal fungi greatly enhance a plant's ability to absorb these nutrients, particularly phosphorus, which is a vital component of energy transfer in plants.
The enhanced nutrient uptake from the plant-fungal relationship positively impacts the plant's growth, yield, and reproductive success.

• Phosphorus: Vital nutrient, often provided by fungal partners.
• Increased nutrient efficiency and absorption.
• Improved plant growth and overall health.

This intricate balance of supply and demand highlights the importance of plant nutrition and its dependency on external support systems like mycorrhizal fungi. It emphasizes the complexity and efficiency of natural nutrient acquisition strategies.