Definitions [5]
Define the term growth.
Growth is characterised as an essential process that results in permanent and irreversible changes to the shape, size, form, weight, and volume of a cell, organ, or entire organism, along with an increase in dry matter.
Differentiation is the process by which unspecialised cells become specialised and take on specific functions.
The living differentiated cells, that have lost the capacity to divide, can regain the capacity of division under certain conditions. This phenomenon is termed as dedifferentiation.
Re-differentiation is the process by which dedifferentiated cells regain specialised characteristics and functionality.
Define the term development.
In the life history of a cell, organ, or organism, development can be defined as a process that involves growth, differentiation, and maturation in a predictable sequence, such as seed germination, growth differentiation, flowering, seed production, and senescence.
Key Points
- Plant growth is seen in roots, stems, leaves, flowers, fruits, and seeds.
- Life stages: seed → seedling → plantlet → mature plant.
- Trees grow continuously, but leaves, flowers, and fruits have limited growth.
- Development includes growth and differentiation from a zygote.
- Germination starts growth in favourable conditions and depends on internal and external factors.
- Plant growth is indeterminate because it continues throughout life due to meristems.
- Meristematic cells keep dividing, and their daughter cells later differentiate to form plant parts.
- Continuous formation of new cells by meristems is called open growth.
- Apical meristems in roots and shoots cause primary growth (increase in length).
- Lateral meristems (in dicots and gymnosperms) cause secondary growth (increase in girth).
| Process | Description | Example |
|---|---|---|
| Differentiation | Cells mature permanently and lose capacity to divide. | Parenchyma develops schizogenous interspaces in hydrophytes. |
| Dedifferentiation | Mature cells regain capacity to divide as per need. | Interfascicular cambium & cork cambium from parenchyma. |
| Redifferentiation | Dedifferentiated cells again lose the capacity to divide and mature for specific function. | Secondary xylem & phloem from cambium. |
