Problem 101 - Objective Biology for NEET

Question

In plant cells, cytokinesis occurs by (a) Furrowing (b) Invagination (c) Anticlinal division (d) Cell plate formation

Step-by-Step Solution

Answer

In plant cells, cytokinesis occurs by (d) Cell plate formation

Step 1: Understanding Cytokinesis in Plant Cells

Cytokinesis refers to the division of the cytoplasm during cell division. In plants, cytokinesis occurs differently than in animal cells because plant cells have a rigid cell wall. Instead of using a cleavage furrow to pinch the cell in half as seen in animal cells, plant cells utilize a different mechanism known as cell plate formation.

Step 2: Explanation of Correct Answer

In plant cells, during cytokinesis, a cell plate is formed in the center of the cell. This cell plate eventually develops into a new cell wall, effectively dividing the two new cells. Hence, the correct answer is that cytokinesis in plant cells occurs via cell plate formation.

Key Concepts

Cell Plate Formation

Cell plate formation is a vital part of plant cell cytokinesis. It is a unique process that distinguishes plant cell division from that of animal cells. Since plant cells have rigid cell walls that cannot be pinched in, they rely on the formation of a cell plate to separate into two new cells.
During cytokinesis, vesicles from the Golgi apparatus accumulate at the center of the dividing cell. These vesicles coalesce to form the cell plate. Over time, this plate expands outward until it fuses with the existing cell walls. The new cell wall separates the two daughter cells, ensuring that they each have their own defined boundary.

• Vesicles form and align in the middle of the cell.
• They merge to create the initial cell plate.
• The plate grows and attaches to the parent cell wall.

This process is critical for maintaining the structural integrity and size consistency of plant cells after division.

Plant Cell Division

Plant cell division includes not only cytokinesis but also mitosis. Mitosis is the process through which the nucleus divides, and it is typically completed before cytokinesis takes place. Plant cells undergo a series of carefully regulated steps to ensure accurate division and distribution of genetic material.
Mitosis in plant cells is generally similar to that in animal cells, involving stages such as prophase, metaphase, anaphase, and telophase. However, the cytokinesis phase in plant cells differs due to the presence of a rigid cell wall, necessitating the formation of the cell plate.

• Prophase: Chromosomes condense and mitotic spindle begins to form.
• Metaphase: Chromosomes align at the cell's equator.
• Anaphase: Chromosomes are pulled apart to opposite poles of the cell.
• Telophase: Nuclear membranes start to re-form around the separated chromosomes.

Following these steps, cytokinesis completes the division process, resulting in two separate plant cells.

Comparative Cytokinesis Methods

Comparing cytokinesis in plant and animal cells reveals some fascinating differences due to their structural characteristics. While plant cells use cell plate formation, animal cells divide through a method known as cleavage furrowing.
In animal cells, microfilaments constrict to create a cleavage furrow that pinches the cell in two. This process is aided by the flexibility of the plasma membrane, which can easily constrict and shape itself during division.
Plant cells, conversely, do not have this flexibility. Their rigid cell walls necessitate a different approach. The cell plate formation method ensures that the newly forming daughter cells are properly separated by a new cell wall, maintaining the rigidity and structural consistency typical of plant cells.

• Animal cells utilize cleavage furrows for division.
• Plant cells rely on cell plate for cytokinesis.
• The choice of method is dictated by the requirement to maintain cell structure.

Understanding these differences not only highlights the adaptability of eukaryotic cells but also emphasizes the importance of cellular structures in dictating division strategies.