Problem 26 - Biology

Question

Which of these occurs through symbiotic nitrogen fixation? a. The plant benefits from using an endless source of nitrogen. b. The soil benefits from being naturally fertilized. c. Bacteria benefit from using photosynthates from the plant. d. All of the above occur.

Step-by-Step Solution

Answer

d. All of the above occur.

Step 1 - Understand Symbiotic Nitrogen Fixation

Symbiotic nitrogen fixation is a mutualistic relationship where bacteria (usually Rhizobium species) live in the root nodules of leguminous plants. The bacteria fix atmospheric nitrogen into a form that the plant can use. In return, the plant supplies the bacteria with carbohydrates produced through photosynthesis.

Step 2 - Evaluate Each Option

Evaluate options to see which benefits stem from symbiotic nitrogen fixation:a. The plant benefits by obtaining nitrogen in a usable form from the bacteria.b. The soil benefits as extra nitrogen can be released, enhancing its fertility.c. Bacteria benefit from the plant’s photosynthates, which serve as energy sources.

Step 3 - Identify Which Option is Correct

Given that all the options point to benefits for different participants in the symbiosis (plant, soil, bacteria), the correct answer is that all of these benefits occur.

Step 4 - Select the Correct Answer

Based on the evaluation, select 'd. All of the above occur' as the correct answer.

Key Concepts

mutualistic relationship

A mutualistic relationship is a type of symbiosis where both parties involved benefit. In the case of symbiotic nitrogen fixation, the partnership is between Rhizobium bacteria and leguminous plants. Both organisms gain significant advantages from this relationship, making it a classic example of mutualism.
Bacteria get a steady supply of food in the form of carbohydrates from the plant. These carbohydrates are produced through the process of photosynthesis.
On the other hand, the plant gets access to nitrogen in a usable form. This nitrogen is essential for its growth and development but is often lacking in the soil.

Rhizobium bacteria

Rhizobium bacteria are a group of soil bacteria that play a crucial role in nitrogen fixation. They enter into a symbiotic relationship with leguminous plants.
These bacteria infect the roots of the plants, leading to the formation of specialized structures known as root nodules. Inside these nodules, the bacteria convert atmospheric nitrogen (N₂) into ammonia (NH₃), a form that plants can readily absorb and use.
This process is beneficial for both the bacteria and the plant. The bacteria receive nutrients and a protective niche within the plant roots, while the plant gains access to nitrogen, which is vital for synthesizing proteins and other important molecules.

leguminous plants

Leguminous plants include beans, peas, lentils, and clover, among others. These plants are unique because they can establish symbiotic relationships with Rhizobium bacteria for nitrogen fixation.
The presence of Rhizobium bacteria in their root nodules allows these plants to grow in nitrogen-poor soils.
This capability makes them important for soil health, as they can naturally replenish soil nitrogen levels, reducing the need for synthetic fertilizers.
Additionally, leguminous plants are often used in crop rotation practices to maintain soil fertility and health over multiple growing seasons.

nitrogen fixation

Nitrogen fixation is the process of converting atmospheric nitrogen (N₂) into ammonia (NH₃) or other molecules that plants can absorb and use.
This process is essential because nitrogen is a critical nutrient for plant growth, but atmospheric nitrogen is not directly usable by plants.
In symbiotic nitrogen fixation, Rhizobium bacteria carry out this conversion in the root nodules of leguminous plants.
The ammonia produced is then assimilated by the plants to form amino acids, proteins, and other nitrogen-containing compounds, supporting plant growth and productivity.
This process also enriches the soil with nitrogen, benefiting subsequent plantings and improving overall soil health.