1. Plant Growth and Development
Regulation of
Plant Growth and Development

2. Growth in Animals Animals grow throughout the whole organism
many regions & tissues at different rates

3. Growth in Plants Specific regions of growth: meristems
stem cells: perpetually embryonic tissue
regenerate new cells
apical shoot meristem
growth in length
primary growth
apical root meristem
lateral meristem
growth in girth
secondary growth

4. Apical meristems
shoot
root

5. Root structure & growth
protecting the meristem

6. protecting the meristem
Shoot growth
Apical bud & primary growth of shoot
region of stem growth
axillary buds
“waiting in the wings”
protecting the meristem
Young leaf
primordium
Apical meristem
Older leaf
primordium
Lateral bud
primordium
Vascular tissue

7. 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

8. 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

9. 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

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

11. 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?

12. Plant hormones
auxin
gibberellins
abscisic acid
ethylene
cytokinins

14. Auxin (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
apical dominance

15. Used as “rooting hormone”
Auxin on roots
Used as “rooting hormone”

16. Cytokinins -made in roots and travel upwards
Effect of cytokinins and lack of auxin

17. 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

18. Gibberellins
- Made in apical meristems (roots and shoots) and developing seeds
-shows effect of ‘”bolting” of flower producing stem

19. Gibberellins
- Made in apical meristems (roots and shoots) and developing seeds
-shows effect of ‘”bolting” of flower producing stem

20. Abscisic acid (ABA) Effects slows growth stimulates closing of
stomata (K+transport out of guard cells)
seed dormancy
high concentrations of abscisic acid
germination only after ABA is inactivated or leeched out
survival value: seed will germinate only under optimal conditions
light, temperature, moisture

21. Ethylene Hormone gas released by plant cells Effects fruit ripening
leaf drop
like in Autumn
apoptosis

22. Fruit ripening Adaptation Mechanism
hard, tart fruit protects developing seed from herbivores
ripe, sweet, soft fruit attracts animals to disperse seed
Mechanism
triggers ripening process
breakdown of cell wall
softening
conversion of starch to sugar
sweetening
positive feedback system
ethylene triggers ripening
ripening stimulates more ethylene production

23. Tropisms

24. Negative gravitropism
Positive gravitropism
Unequal distribution of organelles

26. Thigmotropism

27. Sudden movements caused by sudden release of K+
Response is transmitted to other leaves via action potentials

28. May be related to cyclic concentrations in a transcription factor
Circadian
Rhythms
May be related to cyclic concentrations in a transcription factor

29. Photoperiod and control of flowering
Relative length of day and night

30. Red is most effective in interrupting flowering
A flash of far red can reverse the effect of red

31. Sunlight has high amount of red light cytochrome in Pfr by sunset
Phytochromes photoreceptors that function in a plants response of flowering, germination
Have 2 forms: 1 absorbs red light (Pr), the other far red light (Pfr)
Sunlight has high amount of red light
cytochrome in Pfr by sunset
Need minimum amount of night to covert back to Fr to trigger flowering