Primary growth and secondary growth are two types of plant growth that help a plant increase in size, but they differ in direction, tissues involved, and where they occur.
Here’s the difference explained simply:
- Primary Growth:
- What it is: Growth that makes a plant longer or taller.
- Where it occurs: In the apical meristems (tips of roots and shoots).
- Purpose: Helps the plant increase in length and form new leaves and branches.
- Found in: All plants (both monocots and dicots).
- Example: Growth of root tips to explore more soil or elongation of stems to reach light.
- Secondary Growth:
- What it is: Growth that makes a plant thicker or wider.
- Where it occurs: In the lateral meristems—the vascular cambium and cork cambium.
- Purpose: Increases the girth (diameter) of stems and roots and forms wood and bark.
- Found in: Mostly dicots and gymnosperms, not in most monocots.
- Example: Formation of tree trunks and annual rings in woody plants.
In short:
- Primary growth = Lengthwise growth (by apical meristem)
- Secondary growth = Thickness growth (by lateral meristem)