1. Preprophase Band Formation:
- During the prophase stage of mitosis or meiosis, a preprophase band forms across the dividing plant cell.
- This band is made of microtubules and marks the future plane of cell division.
2. Phragmoplast Formation:
- As the cell enters metaphase, the phragmoplast begins to form.
- It consists of numerous vesicles derived from the Golgi apparatus and contains cell wall components.
- The phragmoplast is positioned at the preprophase band and separates the dividing cell's cytoplasm.
3. Vesicle Fusion and Cell Plate Initiation:
- The phragmoplast vesicles transport cell wall materials, such as cellulose, hemicellulose, and pectin.
- These vesicles fuse with each other, forming a sheet-like structure called the cell plate.
- The cell plate grows outward from the center of the cell towards the cell periphery.
4. Cellulose Deposition and Cell Wall Formation:
- The cell plate consists of two membranes with cellulose synthase (a membrane-bound enzyme complex) between them.
- The cellulose synthase complex synthesizes cellulose microfibrils, which are deposited as a scaffold between the two membranes.
- These cellulose microfibrils intertwine to form a primary cell wall.
5. Cell Plate Expansion:
- The cell plate expands further, dividing the cytoplasm into two daughter cells.
- As the cell plate expands, more cell wall material is deposited, reinforcing the primary cell wall.
6. Secondary Cell Wall Formation:
- After cell division is complete, some plant cells may undergo additional deposition of cell wall material.
- This additional layer is known as the secondary cell wall.
7. Middle Lamella Formation:
- In the space between the primary cell walls of adjacent daughter cells, a middle lamella is formed.
- The middle lamella is composed of pectic substances, further cementing the cells together.
The sequential steps of cell division in plants, including cell wall formation and assembly, ensure proper compartmentalization, growth, and development of the plant organism.
