Problem 76 - Objective Biology for NEET

Question

Bryophytes requires for fertilization (a) Nutrients (b) Water (c) Both (a) and (b) (d) None of these

Step-by-Step Solution

Answer

The answer is (b) Water

Step 1 Identify the Role of Nutrients

The first characteristic to consider is 'nutrients'. Nutrients provide energy and the building blocks for growth and reproduction, and they are vital for the survival of any organism including Bryophytes. However, nutrients are not directly involved in the process of fertilization.

Step 2 Identify the Role of Water

Now consider 'water'. Water is indeed essential for fertilization in Bryophytes because their sperm is motile and needs water to swim to the egg for fertilization.

Step 3 Make a Conclusion Based on the Analysis

Based on steps 1 and 2, it is concluded that while nutrients are necessary for the overall survival and growth of Bryophytes, they are not directly involved in the process of fertilization. On the other hand, water is directly needed for the fertilization process in Bryophytes.

Key Concepts

Nutrient role in plant life

Nutrients play a vital role in the life of all plants, including bryophytes, by providing the necessary materials for growth and development. These essential elements can be grouped into macronutrients like nitrogen, phosphorus, and potassium, and micronutrients such as iron and zinc.

• **Macronutrients**: These are required in larger quantities and are crucial for forming structures like chlorophyll and maintaining cellular functions.
• **Micronutrients**: Although needed in smaller amounts, they are essential for enzyme functions and overall plant health.

Bryophytes, which include mosses and liverworts, absorb nutrients from their surroundings through their entire surface. This adaptation is necessary since they lack root systems like those of higher plants. While nutrients support bryophyte survival, growth, and reproduction by providing energy and the building blocks for cell structures, they are not directly implicated in the fertilization process itself.

Water's role in reproduction

Water is crucial for the reproductive process in bryophytes. These plants rely on a film of water to facilitate fertilization due to the motile nature of their sperm cells. Here’s how water assists in this process:

• **Motility**: Bryophyte sperm are equipped with flagella, enabling them to swim. Water acts as a medium through which sperm can move towards the egg cell.
• **Transfer medium**: The presence of surface water allows for the necessary sperm movement across the plant structure to reach female reproductive organs where eggs are located.

In environments where water is limited, bryophytes face challenges in completing their reproductive cycle. This is why they are often found in moist habitats. Therefore, water serves not just supplementary, but an integral role in bryophyte fertilization.

Bryophyte reproductive biology

The reproductive biology of bryophytes is unique among plants, involving both sexual and asexual methods. Sexual reproduction in bryophytes requires water and results in the production of spores. Here are key components of their reproductive cycle:

• **Gametophyte Phase**: The dominant phase in the bryophyte life cycle, during which the plant is typically visible and active in photosynthesis. This phase produces gametes (sperm and egg).
• **Sporophyte Phase**: This arises post-fertilization; the zygote develops into a sporophyte, which remains attached to the gametophyte, producing spores through meiosis.
• **Spore Dispersal**: Spores are released into the environment, where if conditions are favorable, they will germinate into new gametophytes.

Asexual reproduction occurs through fragmentation, where parts of the gametophyte can form new plants independently. Overall, bryophytes exhibit a sophisticated reproductive strategy, deeply intertwined with their ecological niches and water dependence for sexual reproduction.