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1. Primary & Secondary Growth
Apical & Lateral Meristem
Plant Biology Part 3 - Growth

2. Type of Growth
 Primary growth: grow in length
 Secondary or lateral growth: grow in girth
(diameter, width)

3. Primary Growth
 Increase height for better clearance to
sunlight
 Roots burrow deep into soil to access
nutrients and for structural stability
 Occurs in:
 Herbaceous plants
 Young plants
 Tips of roots and shoots of woody plants

4. Meristematic Cells (Meristem)
 Undifferentiated
plant cells
 2 types:
 Apical
 Lateral

5. Apical Meristem
 Undifferentiated
cells at the tips of
plant roots and
shoots (buds)
 Cells that divide
enable the plant to
grow longer
(deeper into the
ground, and taller)

6. Root Apical
Meristem

7. Root Zones
 Zone of maturation: cells
differentiate into different
types of cells
 Zone of elongation: allows
the root to get deeper
within the soil
 Meristematic region: rapid
mitosis of undifferentiated
meristematic cells
 Root cap: protects the
meristematic region

8. Shoot Apical Meristem
 Located in buds
 Terminal / Apical
bud: at the tip of a
growing stem
 Axillary / Lateral
bud: at points along
the stem where
lateral branches form
Terminal /
Apical bud
Axillary /
Lateral bud

9. Shoot Apical Meristem
http://www.uwgb.edu/biodiversity/herbarium/trees/axillary_lateral_bud02.jpghttp://www.fs.fed.us/pnw/olympia/silv/local-resources/glossary/images/apical.jpg

10. Apical Dominance
 Terminal bud inhibits the growth of axillary bud
 What advantage does this provide for the
plant?

11. Apical Dominance
 What would happen to plant growth if the
terminal bud was cut off?
 Explain why pruning shrubs makes them busier.

12. Apical Dominance
http://www.mun.ca/biology/desmid/brian/BIOL3530/DB_12/fig12_13.jpg

14. Secondary / Lateral Growth
 Thickening of roots and shoots
 Adds strength to plant structure
 Growth due to lateral meristem
 Never occurs in leaves
 Occurs in mature part of woody plants

15. Secondary Growth
 Accounts for the rings
formed in tree trunks

16. http://www.uic.edu/classes/bios/bios100/labs/vasccamb.jpg

17. Lateral Meristem
 Cork Cambium
 Outer lateral meristem
 Makes dermal tissue called cork / periderm  bark
 Vascular Cambium
 Inner lateral meristem
 Outer surface makes phloem  bark
 Inner surface makes xylem  reason for growth,
creates the tree rings seen in trunks of woody
plants

18. Comparing Plant Growth
Growth Effect Meristem
Primary Height
deep roots
Root Apical meristem
Shoot Apical meristem
apical/terminal bud
axillary/lateral bud
Secondary /
Lateral
Width / girth Lateral meristem
Cork cambium
Vascular cambium