Problem 147 - Objective Biology for NEET

Question

Coralloid roots having association with \(\mathrm{N}_{2}\) fixing bacteria are found in (a) Pinus (b) Cedrus (c) Sequoia (d) Cycas

Step-by-Step Solution

Answer

The correct answer is (d) Cycas. This plant possesses Coralloid roots having an association with \(\mathrm{N}_{2}\) fixing bacteria.

Step 1: Understanding Symbiotic Association

Coralloid roots are known to have a symbiotic association with \(\mathrm{N}_{2}\) fixing bacteria (also known as nitrogen-fixing bacteria). These bacteria can convert inert atmospheric nitrogen into forms that are usable by the plants. This kind of symbiotic association is beneficial for both the plant and the bacteria.

Step 2: Identifying the Correct Plant

Knowing the different types of roots in various plant species helps in identifying the correct option. Among the choices given: Pinus, Cedrus, Sequoia, and Cycas, it is known that Coralloid roots having association with \(\mathrm{N}_{2}\) fixing bacteria are found in the plant Cycas.

Key Concepts

N2 fixing bacteria

Nitrogen-fixing bacteria play a crucial role in the environment by transforming atmospheric nitrogen, which is as inert as a sleeping giant, into a form that plants can absorb and use. This process is essential because nitrogen is a vital nutrient for plant growth, but most plants cannot take it directly from the air. These bacteria form mutualistic relationships with plants, meaning both benefit from the association. They inhabit special root structures, such as coralloid roots in some plants, and convert nitrogen gas into ammonia. This ammonia is then converted into forms like nitrate or nitrite, which plants can readily use. This is especially important in nutrient-poor soils where nitrogen is scarce. The presence of these bacteria not only improves soil fertility but also helps in sustainable agriculture by reducing the need for chemical fertilizers.

Symbiotic association

Symbiotic association between plants and nitrogen-fixing bacteria is a mutually beneficial relationship. In such an alliance, plants provide the bacteria with carbohydrates for energy. In return, bacteria provide the plant with essential nutrients. This collaboration is similar to a team effort, each player doing their part for mutual gain.
Coralloid roots, found in certain plants, are unique because they facilitate this partnership. They provide a habitat for the bacteria, while the bacteria enhance the plant’s nutrient uptake. This association was evolutionary genius, allowing certain plants to thrive in environments where others couldn’t.

• Mutual benefits: both plant and bacteria gain from the relationship.
• Nutrient exchange: bacteria receive energy, while the plant gets nutrients.
• Adaptive advantage: this association allows plants to survive in nitrogen-poor soils.

Understanding this association helps us appreciate the complexity and brilliance of nature's designs.

Cycas

Cycas is a genus of plants that holds a unique spot in the plant kingdom. They are classified as gymnosperms and are often mistaken for palms, though they are unrelated. One remarkable feature of Cycas plants is their coralloid roots. These roots have a peculiar, coral-like appearance and are a classic example of nature's design for survival.
Coralloid roots in Cycas form a symbiotic relationship with nitrogen-fixing bacteria. This feature enables Cycas to grow in environments that lack nitrogen availability. They are like nature's own nitrogen fertilizer, allowing the plant to thrive even in poor soil conditions. This adaptation is particularly beneficial for Cycas, as they often grow in sandy and infertile ground, where other plants might struggle.
Key points about Cycas:

• They are not palms but belong to gymnosperms.
• Coralloid roots enable symbiotic association with nitrogen-fixing bacteria.
• Adapted to thrive in nutrient-poor environments.

Cycas plants embody resilience and resourcefulness, showcasing the fascinating interplay between plant structure and function.