1. Introduction
Plant tissue culture relies on cell growth and division for callus formation, shoot regeneration, and root development. Cells divide following a structured pattern, which includes:
- The cell cycle (G1, S, G2, M phase).
- The growth phases (lag, exponential, stationary, decline).
- Mitosis, where new identical cells are produced.
This lesson explores these phases, why they matter in tissue culture, and how scientists control them.
📌 Further Reading:
- Cell Growth and Division in Plants
- Mitosis in Plant Tissue Culture
2. The Cell Cycle: How Plant Cells Divide
Plant cells follow a cell cycle that regulates growth and division.
2.1 Stages of the Cell Cycle
| Stage | What Happens? |
|---|---|
| G1 Phase | Cell grows, prepares for DNA replication. |
| S Phase | DNA replication occurs, doubling genetic material. |
| G2 Phase | Prepares for mitosis, cell checks for errors. |
| M Phase (Mitosis) | Cell divides into two identical daughter cells. |
📌 Further Reading: Plant Cell Cycle Regulation
3. Phases of Cell Growth in Tissue Culture
When plant cells are cultured, they follow distinct growth phases:
3.1 Lag Phase (Adaptation)
- Cells adjust to their new environment.
- Little to no division occurs.
- Cells activate metabolism for growth.
3.2 Exponential Phase (Rapid Division)
- Cells divide rapidly via mitosis.
- Growth is at its highest rate.
- Callus tissue expands quickly.
3.3 Stationary Phase (Slowing Down)
- Cells stop dividing as nutrients decrease.
- Some cells begin differentiating into plant tissues.
3.4 Decline Phase (Cell Death)
- Cells start dying as nutrients are depleted.
- Older cultures may need to be transferred to fresh medium.
📌 Further Reading: Cell Growth Stages in Tissue Culture
4. The Mitotic Phase: Producing New Cells
Mitosis ensures that tissue culture cells divide and regenerate properly.
4.1 Steps of Mitosis
| Phase | Description |
|---|---|
| Prophase | Chromosomes condense, spindle fibers form. |
| Metaphase | Chromosomes align in the center. |
| Anaphase | Chromosomes separate to opposite ends. |
| Telophase | New cell nuclei form. |
| Cytokinesis | The cell fully divides into two. |
📌 Further Reading: Mitosis and Plant Growth
5. Factors Affecting Cell Division in Tissue Culture
Scientists optimize cell division rates by controlling key factors:
-
Plant Growth Regulators (PGRs)
- Auxins promote cell elongation.
- Cytokinins stimulate mitosis.
-
Nutrient Availability
- MS Medium provides essential minerals.
- Sugar serves as an energy source.
-
Light and Temperature
- Some cultures need light for differentiation.
- 25-28°C is optimal for most plant cells.
-
Oxygen Supply
- Proper aeration improves cell metabolism.
📌 Further Reading: Optimizing Cell Division in Tissue Culture