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 Cycle
Diploid
Double fertilization
Meiosis
Meiosis
Haploid
Mitosis without cytoplasmic division
microspores
pollination
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 photosynthesis
carries out reproduction
Shoot System
Root system
anchors the plant
penetrates the soil and absorbs water and minerals
stores food
Root System

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

7. Plant Tissue Systems Ground tissue system Vascular tissue system
EPIDERMIS
Ground tissue system
Vascular tissue system
Dermal tissue system
VASCULAR TISSUES
GROUND TISSUES
SHOOT SYSTEM
ROOT 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: SAM and RAM
activity at
meristems
Cells that form at apical meristems:
new cells
elongate
and start to
differentiate
into primary
tissues
protoderm  epidermis
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. Made up of only one type of cell
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. Composed of a mix of cell types
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
Companion cells assist in the loading of sugars
sieve-tube
member
companion
cell

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
4 or 5 floral parts
3 floral parts
Netlike veins
Parallel veins
3 pores
1 pore
Vascular bundles dispersed
Vascular bundles in ring

21. Shoot Development shoot apical meristem protoderm procambrium
ground meristem
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 of a Monocot Stem
The vascular bundles are distributed throughout the ground tissue
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 EPIDERMIS cuticle PALISADE MESOPHYLL xylem SPONGY
phloem
LOWER
EPIDERMIS
CO2
one stoma O2

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 meristem
root cap

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
Both increase the surface 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
new
lateral
root

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 cork, cork cambium,
and secondary cortex)
secondary
phloem
HEARTWOOD
SAPWOOD
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) Softwood (pine, redwood)
Dicot wood
Xylem composed of vessels, tracheids, and fibers
Softwood (pine, redwood)
Gymnosperm wood
Xylem composed mostly of tracheids
Grows more quickly