2nd year

1. March 28, 2005
Plant Tissues
Chapter 26
Jin Hoe Huh

2. Angiosperms – flowering plants
• The angiosperms are seed-bearing
vascular plants
• In terms of distribution and diversity,
they are the most successful plants on
Earth
• The structure and function of this plant
group help explain its success

3. Flowering
Plant Life Double fertilization
Diploid
Meiosis Meiosis
Cycle
Haploid
Mitosis
without
microspores
pollination cytoplasmic
division
Two
sperms
enter
ovule Female gametophyte

4. Plant Life Histories
• Annuals complete life cycle in one
growing season
• Biennials live for two seasons; flowers
form in second season
• Perennials grow and produce seeds
year after year

5. Shoot and Root
Systems
Shoot system
- produces sugars by Shoot
photosynthesis System
- carries out reproduction
Root system
- anchors the plant
- penetrates the soil and Root
absorbs water and minerals System
- stores food

6. Shoot and root
systems are
interdependent
water &
sugar
minerals
SHOOT SYSTEM
ROOT SYSTEM

7. Plant Tissue
Systems EPIDERMIS
• Ground tissue VASCULAR TISSUES
system
• Vascular tissue
GROUND TISSUES
system
SHOOT SYSTEM
• Dermal tissue
ROOT SYSTEM
system

8. Meristems – Where Tissues Originate
• Regions where cell divisions produce
plant growth
• Apical meristems
– Lengthen stems and roots
– Responsible for primary growth
• Lateral meristems
– Increase width of stems
– Responsible for secondary growth

9. Apical Meristems
Lengthen shoots and roots: activity at
meristems
SAM and RAM
Cells that form at apical new cells
elongate
meristems: and start to
differentiate
protoderm  epidermis into primary
tissues
ground meristem  ground
tissues
procambium  primary
vascular tissues

10. Lateral Meristems
Increases girth of older roots and stems
Cylindrical arrays of cells
vascular cambium  secondary vascular tissues
periderm  cork cambium
thickening

11. Simple Tissues
Made up of only one
type of cell
Parenchyma
Collenchyma
Sclerenchyma

12. Morphology of three simple tissue types
parenchyma collenchyma sclerenchyma

13. Parenchyma: A Simple Tissue
• Comprises most of a plant’s soft primary growth
• Cells are pliable, thin walled, many sided
• Cells remain alive at maturity and retain
capacity to divide
• Mesophyll is a type of parenchyma that
contains chloroplasts

14. Collenchyma: A Simple Tissue
• Specialized for support for primary tissues
• Cells are elongated, with walls (especially
corners) thickened with pectin
• Makes stems strong but pliable
• Cells are alive at maturity

15. Sclerenchyma: A Simple Tissue
• Supports mature plant parts
• Protects many seeds
• Cells have thick, lignified walls and are dead
at maturity
• Two types:
– Fibers: Long, tapered cells
– Sclereids: Stubbier cells

16. Complex Tissues
Composed of a mix of cell types
Xylem
Phloem
Epidermis

17. Xylem
• Conducts water
and dissolved
minerals
• Conducting cells
are dead and
hollow at maturity
vessel
member
tracheids

18. Phloem:
A Complex Vascular Tissue
sieve plate
• Transports sugars
• Main conducting
cells are sieve-
tube members
sieve-tube
• Companion cells member
companion
assist in the cell
loading of sugars

19. Epidermis:
A Complex Plant Tissue
- Covers and protects plant
surfaces
- Secretes a waxy,
waterproof cuticle
- In plants with secondary
growth, periderm replaces
epidermis

20. Monocots and Dicots – same
tissues, different features
1 cotyledon 2 cotyledons
3 floral 4 or 5 floral
parts parts
Netlike veins
Parallel veins
1 pore 3 pores
Vascular Vascular
bundles bundles
in ring dispersed

21. shoot apical
meristem
Shoot protoderm procambrium ground meristem
Development
cortex procambrium pith primary xylem primary phloem

22. Bud = undeveloped shoot of
meristematic tissue
Leaves
Internode
Axillary bud at node
Longitudinal section of terminal bud

23. Roots also have meristems

24. Internal Structure of a
Dicot Stem
- Outermost layer is epidermis
- Cortex lies beneath epidermis
- Ring of vascular bundles
separates the cortex from the pith
- The pith lies in the center of the
stem

25. Internal
Structure
• The vascular bundles
of a are distributed
Monocot throughout the ground
tissue
Stem • No division of ground
tissue into cortex and
pith

26. Dicots Monocots
Ground tissue
system
Dermal tissue
system
Vascular tissue
system
Dicots and Monocots have different stem and root anatomies

27. Leaf Gross Structure
DICOT MONOCOT
petiole
axillary
bud
blade
node
sheath
blade
node

28. Adapted for Photosynthesis
• Leaves are usually thin
– High surface area-to-volume ratio
– Promotes diffusion of carbon dioxide in,
oxygen out
• Leaves are arranged to capture sunlight
– Are held perpendicular to rays of sun
– Arrange so they don’t shade one another

29. Leaf Structure
UPPER
cuticle EPIDERMIS
PALISADE
MESOPHYLL
xylem
SPONGY
MESOPHYLL
phloem
LOWER
EPIDERMIS
O2 CO2 one stoma

30. Mesophyll:
Photosynthetic Tissue
• A type of parenchyma tissue
• Cells have chloroplasts
• Two layers in dicots
– Palisade mesophyll
– Spongy mesophyll

31. Collenchyma
Parenchyma

32. Leaf Veins: Vascular Bundles
• Xylem and phloem –
often strengthened with fibers
• In dicots, veins are netlike
• In monocots, they are parallel

33. Root Systems

34. Root Structure
• Root cap covers tip
• Apical meristem produces
the cap
• Cell divisions at the apical
meristem cause the root to
lengthen
• Farther up, cells
differentiate and mature
root apical root cap
meristem

35. Internal Structure of a Root
• Outermost layer is epidermis
• Root cortex is beneath the epidermis
• Endodermis, then pericycle surround
the vascular cylinder
• In some plants, there is a central pith

36. epidermis
endodermis
cortex
pericycle
root hair
phloem
xylem

37. Root Hairs and Lateral Roots
new
• Both increase the surface lateral
root
area of a root system
• Root hairs are tiny extensions
of epidermal cells
• Lateral roots arise from the
pericycle and must push
through the cortex and
epidermis to reach the soil

38. Secondary Growth
• Occurs in perennials
• A ring of vascular cambium produces
secondary xylem and phloem
• Wood is the accumulation of these
secondary tissues, especially xylem

39. Secondary Growth

40. Woody Stem
periderm (consists of secondary HEARTWOOD SAPWOOD
cork, cork cambium, phloem
and secondary cortex)
BARK
vascular cambium

41. Annual Rings
• Concentric rings of secondary xylem
• Alternating bands of early and late
wood
• Early wood
– Xylem cells with large diameter, thin walls
• Late wood
– Xylem cells with smaller diameter, thicker
walls

42. Types of Wood
• Hardwood (oak, hickory)
– Dicot wood
– Xylem composed of vessels, tracheids,
and fibers
• Softwood (pine, redwood)
– Gymnosperm wood
– Xylem composed mostly of tracheids
– Grows more quickly