1. Plant Structure Growth and Development
Chapter 35

2. Evolution of Plants All Plants…
multicellular, eukaryotic, autotrophic, alternation of generations

3. Alternation of Generations
Sporophyte (diploid)
produces haploid
spores via meiosis
Gametophyte (haploid)
produce haploid
gametes via mitosis
Fertilization
joins two gametes to
form a zygote

4. Angiosperms Monocots vs. Dicots named for the number
of cotyledons (seed leaf) present on
the embryo of the plant
+ monocots
- orchids, corn,
lilies, grasses
+ dicots
- roses, beans,
sunflowers, oaks

5. Plant Morphology Morphology (body form) shoot and root systems
+ inhabit two environments
- shoot (aerial)
+ stems, leaves, flowers
- root (subterranean)
+ taproot, lateral roots
vascular tissues
+ transport materials between
roots and shoots
- xylem/phloem

6. Plant Anatomy Anatomy (internal structure) division of labor
+ cells differing in structure and function
- parenchyma, collenchyma, sclerenchyma (below)
- water- and food-conducting cells (next slide)
Parenchyma
St: “typical” plant cells
Fu: perform most metabolic functions
Collenchyma
St: unevenly thickened primary walls
Fu: provide support but allow growth
in young parts of plants
Sclerenchyma
St: hardened secondary walls
(LIGNIN)
Fu: specialized for support; dead

7. Plant cell types Parenchyma cells Collenchyma cells Cell wall
Sclerenchyma cells

8. Plant cell types Xylem Phloem Vessel Tracheids Tracheids and vessels
WATER-CONDUCTING CELLS OF THE XYLEM
Vessel
Tracheids
Tracheids and vessels
element
Pits
SUGAR-CONDUCTING CELLS OF THE PHLOEM
Companion cell
Sieve-tube
member
Sieve-tube members:
longitudinal view
Sieve
plate
Nucleus
Cytoplasm
Companion
cell

9. Water- and Food-conducting Cells
Xylem (water)
dead at functional maturity
tracheids- tapered with pits
vessel elements- regular tubes
Phloem (food)
alive at functional maturity
sieve-tube members- arranged
end to end with sieve plates &
Companion cells

10. Plant Tissues Three Tissue Systems dermal tissue + epidermis (skin)
- single layer of cells that
covers entire body
- waxy cuticle/root hairs
vascular tissue
+ xylem and phloem
- transport and support
ground tissue
+ mostly parenchyma
- occupies the space b/n
dermal/vascular tissue
- photosynthesis, storage,
support

11. Plant Growth Meristems
perpetually embryonic tissues located at regions of growth
+ divide to generate additional cells (initials and derivatives)
- apical meristems (primary growth- length)
+ located at tips of roots and shoots
- lateral meristems (secondary growth- girth)

12. Roots A root Is an organ that anchors the vascular plant
Absorbs minerals and water
Often stores organic nutrients
Taproots found in dicots and gymnosperms
Lateral roots (Branch roots off of the taproot)
Fibrous root system in monocots (e.g. grass)
Figure 35.3

13. Modified Roots Many plants have modified roots (a) Prop roots
(b) Storage roots
(c) “Strangling” aerial roots
(d) Buttress roots
(e) Pneumatophores
(a) Prop roots
(b) Storage roots

14. Primary Growth of Roots
apical meristem
+ root cap
+ three overlapping zones
- cell division
- elongation
- maturation

15. Stems A stem is an organ consisting of
Nodes (point where leaf connects)
Internodes (stem between nodes)

16. Modified Stems Stolons Storage leaves Rhizomes Stem Node Root Bulbs
Tubers
(c)
Bulbs
Stolons
(a)
Storage leaves
Stem
Root
Node
Rhizome

17. Buds
An axillary bud
Is a structure that has the potential to form a lateral shoot, or branch
A terminal bud
Is located near the shoot tip and causes elongation of a young shoot
Gardening tip:
Removing the terminal bud stimulates growth of axillary buds

18. Primary Growth in Shoots
apical meristem (1, 7)
+ cell division occurs
+ produces primary meristems
- protoderm (4, 8)
- procambium (3, 10)
- ground meristem (5, 9)
axillary bud meristems
+ located at base of
leaf primordia
leaf primordium (2, 6)
+ gives rise to leaves

19. The leaf
Is the main photosynthetic organ of most vascular plants
Leaves generally consist of
Blade
Stalk
Petiole

20. Leaf Morphology In classifying angiosperms
Taxonomists may use leaf morphology as a criterion
Petiole
(a) Simple leaf
(b) Compound leaf.
(c) Doubly
compound leaf.
Axillary bud
Leaflet

21. Modified Leaves Tendrils Spines Storage leaves Bracts
Reproductive leaves. The leaves of some succulents produce adventitious plantlets, which fall off the leaf and take root in the soil.

22. Leaf Anatomy Epidermal Tissue upper/lower epidermis
guard cells (stomata)
Ground Tissue
mesophyll
+palisade/spongy
parenchyma
Vascular Tissue
veins
+ xylem and phloem

23. Cutaway drawing of leaf tissues
Leaf Anatomy
Key
to labels
Dermal
Ground
Vascular
Guard
cells
Stomatal pore
Epidermal
cell
50 µm
Surface view of a spiderwort
(Tradescantia) leaf (LM)
(b)
Cuticle
Sclerenchyma
fibers
Stoma
Upper
epidermis
Palisade
mesophyll
Spongy
Lower
Vein
Xylem
Phloem
Bundle-
sheath
Cutaway drawing of leaf tissues
(a)
Air spaces
Guard cells
100 µm
Transverse section of a lilac
(Syringa) leaf (LM)
(c)

25. The Three Tissue Systems: Dermal, Vascular, and Ground

26. Dermal Tissue Protects plant from: Physical damage Pathogens
H2O loss (Cuticle)

27. Vascular tissue
Carries out long-distance transport of materials between roots and shoots
Consists of two tissues, xylem and phloem
Xylem
Phloem

28. Ground Tissue
Includes various cells specialized for functions such as storage, photosynthesis, and support
Pith = ground tissue internal to the vascular tissue
Cortex = ground tissue external to the vascular tissue

29. Secondary Growth Lateral Meristems vascular cambium
+ produces secondary xylem/phloem (vascular tissue)
cork cambium
+ produces tough, thick covering (replaces epidermis)
secondary growth
+ occurs in all gymnosperms; most dicot angiosperms

30. The Vascular Cambium and Secondary Vascular Tissue
Is a cylinder of meristematic cells one cell thick
Develops from parenchyma cells

31. 2° Growth As a tree or woody shrub ages
The older layers of secondary xylem, the heartwood, no longer transport water and minerals
The outer layers, known as sapwood
Still transport materials through the xylem

32. Cork Cambium Periderm protective coat of secondary plant body
+ cork cambium and
dead cork cells
- bark
cork cambium produces
cork cells