1. Primary Growth and Secondary Growth
The Growth of Plants
Primary Growth and
Secondary Growth

2. Primary Growth
Secondary Growth

3. Primary Growth
Plants grow continuously because they have meristem cells
Undifferentiated cells that retain the ability to undergo Mitosis and hence produce new cells

4. Apical Meristem

5. Primary Growth due to Apical Meristems
Plants have 2 apical meristems:
at the tips of the root &
at the tips of the buds
What is the purpose of Primary Growth?
A process called Primary Growth produces the new cells that allow a plant to grow in length!

6. Meristem cells Meristem cells make 3 types of tissues: Vascular Tissue
Provides support
Transports water, nutrients (Xylem)
Transports photosynthetic products (Phloem)
Ground Tissue
Bulk of plants body
Responsible for photosynthesis
Epidermal Tissue
The “skin”, covering entire plant
protection

8. Dermal, Ground & Vascular Tissue

9. Secondary Growth Increases the width Purpose:
Increase of vascular tissue
Structural support
Secondary Growth produces wood

10. Secondary Growth Has a ring of meristem cells:
Vascular cambium
Produces Xylem &
Phloem tubules
New cells that develop on the outside of the vascular cambium turn into Phloem
New cells that develop on the inside of the cambium vascular turn into Xylem

11. Secondary Growth

12. The Structure of a Tree Trunk

13. 3 main parts … Heartwood Sapwood Bark Dead Provides structural support
Xylem tissue
Bark
Inner bark: Phloem
Outer bark:

14. The Structure of a Tree Trunk
Rays radiate laterally across the Xylem…
Rays move water & nutrients laterally across the stem

15. Let’s draw the structures of a tree trunk …
Heartwood
Vascular cambium
Bark
Xylem
Phloem
Rays

16. Growth Rings … Natural Phenomenon:
The vascular cambium stops the growth during a portion of the year
No growth = dormancy occurs during the winter in cold climates
Growth begins again during the spring season

17. Growth Rings .. 1 growth ring = 1 year Wider rings, good rainy years
Smaller, darker band
Larger, lighter band
Wider rings, good rainy years
Narrow rings, cold, dry years