1. Plant Growth

2. Growth in Animals Animals grow throughout the whole organism
Many regions & tissues at different rates
Growth stops when a certain size or development is reached
Called determinate growth.

3. Growth in Plants Specific regions of growth: meristems
Perpetually embryonic tissue
Cells can divide
indefinitely.
Called indeterminate
growth.

4. Growth in Plants regenerate new cells apical shoot meristem
growth in length
primary growth
apical root meristem
lateral meristem
growth in girth
secondary growth

5. Apical meristems
shoot
root

6. Root structure & growth
protecting the meristem

7. protecting the meristem
Shoot growth
Apical bud & primary growth of shoot
Region of stem growth
Lengthens the shoot
by mitosis and cell division.
Tip of shoot = Apex
protecting the meristem
Young leaf
primordium
Apical meristem
Older leaf
primordium
Lateral bud
primordium
Vascular tissue

8. Growth in woody plants Woody plants grow in height from tip
Primary
xylem
Growth in woody plants
Woody plants grow in height from tip
primary growth
apical meristem
Woody plants grow in diameter from sides
secondary growth
lateral meristems
vascular cambium
makes 2° phloem & 2° xylem
cork cambium
makes bark
Primary
phloem
Epidermis
Lateral
meristems
Secondary
xylem
Primary
phloem
Primary
xylem
Secondary
phloem
Annual
growth
layers
Bark

9. Secondary growth Secondary growth growth in diameter
thickens & strengthens older part of tree
cork cambium makes bark
growing ring around tree
vascular cambium makes xylem & phloem

10. Why are early & late growth different?
Vascular cambium
Phloem produced to the outside
Xylem produced to the inside
bark
phloem
cork cambium
xylem
late
vascular cambium
early
last year’s xylem

11. Woody stem How old is this tree? cork cambium vascular cambium late
early 3 2 1
xylem
phloem
bark

12. Tree trunk anatomy tree girdling What does girdling do to a tree?
Aaaargh!
Murderer!
Arborcide!
Tree trunk anatomy
tree girdling
What does girdling do to a tree?

13. Where will the carving be in 50 years?

14. PLANT HORMONES A. Are chemical signals that coordinate different parts of an organism. B. Require only minute amounts. C. Produced by 1 part of plant body. D. Transported to another part E. Binds to specific receptor F. Triggers response in target cells and tissues.

15. Examples of Plant hormones:
auxin
gibberellins
abscisic acid
ethylene
and more…

16. Auxin (indole-3 acetic acid or IAA)
Effects
controls cell division & differentiation
phototropism
growth towards light
asymmetrical distribution of auxin
cells on darker side elongate faster than cells on brighter side

17. Auxin (indole-3 acetic acid or IAA)
Effects
Apical dominance
Prevents axillary buds
from growing.
These auxins are produced by meristem in shoot apex.

18. Gibberellins Family of hormones Effects
over 100 different gibberellins identified
Effects
stem elongation
fruit growth
seed germination
plump grapes in grocery stores have been treated with gibberellin hormones while on the vine

19. Animal vs. Plant Responses
Comparing responses to stimuli of plants and animals:
A. Animals – Respond to stimuli by changing behavior.
1. Move toward positive stimulus
2. Move away from negative stimulus

20. B. Plants – Respond to stimuli by:
Adjusting growth and development
Plants adjusting their directional growth responses to directional external stimuli (such as light or gravity) are called tropisms.
Response to light is phototropism.
Response to gravity is called gravitropism.
Growth toward a stimulus is a positive tropism.
Growth away from a stimulus is a negative tropism.

21. Auxin influences gene expression in phototropism.
Light is absorbed by photoreceptor proteins called phototropins.
Phototropins change conformation and bind to receptors within the cell.
Receptors control specific genes transcribing plasma membrane proteins which transport auxin.