1. Plant Tissues

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. 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

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

5. 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

6. Meristems – Where Tissues Originate
Regions where cell divisions produce plant growth
Apical meristems
Responsible for primary growth (length)
Lateral meristems
Responsible for secondary growth (width)

7. Apical Meristems Lengthen shoots and roots: StemAM and RootAM
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

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

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

11. Ground Tissue fills space b/t dermis & vascular
 Parenchyma: Primary metabolic function (photosynthesis)
Found in roots, stems & leaves
Least specialized, thin flexible walls, don’t divide unless specializing, respire, store food & water
Schlerenchyma: support w/ thick 2o wall strengthened by lignin
Found in stems & leaves generally lack protoplasts
Very rigid cell wall, dead at maturity, cannot lengthen scaffolding “fibers” & “Sclereids”
Collenchyma: child support
Found in stems and leaves
Grow and elongate with stems and leaves they support, flexible in young parts of plant

12. Morphology of three simple tissue types
parenchyma
collenchyma
sclerenchyma

13. Simple Tissues Complex Tissues Composed of a mix of cell types Xylem
Phloem
Epidermis
Made up of only one type of cell
Parenchyma
Collenchyma
Sclerenchyma

14. Vascular Tissue  
Phloem: Phood conduction, carries products of photosynthesis to non-photo cells
Found in roots, stems, leaves
Sieve cells, albuminous cells, companion cells, parenchyma
Gymnospersm: sieve, angiosperms, sieve-tube members, connected vertically by sieve plates
Alive at maturity
Xylem: provides water & ion transport from roots to leaves
Vessel elements, tracheids, fibers, wood parenchymal
tracheids & vessel members, thick w/ secondary wall with lignin
Dead at maturity
Seedless vascular & gymnosperms have tracheids w/ tapered ends
Angiospersm have both tracheids and vessel members wh are continuous

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

16. 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

17. Epidermis: A Complex Plant Tissue
- Covers and protects plant surfaces
Secretes a waxy, waterproof cuticle
In plants with secondary growth, periderm replaces epidermis
protection, increase absorption area in roots, reduces H2O loss in stem & leaves,
Regulates gas exchange in leaves
Signaling between Plants and Pathogens

18. Shoot and Root Systems: Not independent
Shoot system
produces sugars by photosynthesis
carries out reproduction
water & minerals
sugar
SHOOT SYSTEM
Root system
anchors the plant
penetrates the soil and absorbs water and minerals
stores food
ROOT SYSTEM

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

20. Roots also have meristems

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

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

23. Mesophyll: Photosynthetic Tissue
A type of parenchyma tissue
Cells have chloroplasts
Two layers in dicots
Palisade mesophyll
Spongy mesophyll
Parenchyma
Collenchyma

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

25. 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

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

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

28. Stems
Monocot stems differ from dicot stems in that they lack secondary growth
No vascular cambium nor cork cambium
Stems usually uniform in diameter
Scattered vascular bundles (not in a ring like dicot stems)

29. The Translocation of Phloem
the process of moving photosynthetic product through the phloem
In angiosperms, the specialized cells that transport food in the plant are called sieve-tube members, arranged end to end to form large sieve tubes
Phloem sap is very different from xylem sap
sugar (sucrose) can be concentrated up to 30% by weight
Phloem transport is bidirectional
Phloem moves from a sugar source (a place where sugar is produce by photosynthesis or by the breakdown of sugars) to a sugar sink (an organ which consumes or stores sugar)
What are some organs which would be sugar sinks?
Transport in Plants:
The Pressure Flow Model , 2

30. Root Systems

31. Root Structure Root cap covers tip Apical meristem produces the cap
pericycle
phloem
xylem
root hair
endodermis
epidermis
cortex
Root cap covers tip
Apical meristem produces the cap
Cell divisions and elongation at the apical meristem cause the root to lengthen
Farther up, cells differentiate and mature
root apical meristem
root cap

32. Primary Root Growth Root Cap
Secretes polysaccharide slime that lubricates the soil
Constantly sloughed off and replaced
Apical Meristem
Region of rapid cell division of undifferentiated cells
Most cell division is directed away from the root cap
Quiescent Center
Populations of cells in apical meristem which reproduce much more slowly than other meristematic cells
Resistant to radiation and chemical damage
Possibly a reserve which can be called into action if the apical meristem becomes damaged
The Zone of Cell Division - Primary Meristems
Three areas just above the apical meristem that continue to divide for some time
Protoderm
Ground meristem
Procambium
The Zone of Elongation
Cells elongate up to ten times their original length
This growth pushes the root further downward into the soil
The Zone of Maturation
Region of the root where completely functional cells are found

33. 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

34. Root Anatomy - Dicot Roots
Epidermis
Dermal tissue
Protection of the root
Cortex
Ground tissue
Storage of photosynthetic products
Active in the uptake of water and minerals
Endodermis
cylinder once cell thick that forms a boundary between the cortex and the stele contains the casparian strip,
Pericycle
found just inside of the endodermis
may become meristematic
responsible for the formation of lateral roots
Vascular Tissue
Xylem and Phloem
Root Anatomy - Monocot Roots
cylinder once cell thick that forms a boundary between the cortex and the stele even more distinct than dicot counterpart contains the casparian strip,
monocot roots rarely branch, but can, and this branch will originate from the pericycle
Forms a ring near center of plant
Pith
Center most region of root

35. 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
Root of a single rye plant (fibrous system) measure and counted 6400 roots w/ 12.5 million root hairs = 250 km, dist from Memphis, TN to Atlanta, GA
new
lateral
root

36. Symplastic Movement
Movement of water and solutes through the continuous connection of cytoplasm (though plasmodesmata)
No crossing of the plasma membrane (once it is in the symplast)
Apoplastic Movement
Movement of water and solutes through the cell walls and the intercellular spaces
No crossing of the plasma membrane
More rapid - less resistance to the flow of water

37. Net flow in whole plants
Fig overview of transport in plants
Animation Transpiration Pull (animation ~ 5)

40. Fig b

41. Ascent of xylem sap transpirational pull
flow from greater to lower water concentration
relies on cohesion & adhesion of water
cavitation breaks chain of water molecules
corresponding overheads:
Fig roles of cohesion & adhesion in ascent of xylem sap
Fig control of stomatal opening & closing

42. Fig

43. The availability of soil water and minerals
Animation (animation~4) Mineral uptake in roots
Long-distance transport of water from roots to leaves

44. Net flow in whole plants
Key Concepts:
Diffusion: movement of molecules from high to low concentration.
Osmosis: diffusion of water across a semi-permeable membrane.
Mass or bulk flow: movement of fluid due to pressure or gravity differences.
Fig overview of transport in plants
Animation Transpiration Pull (animation ~ 5)

46. Long-distance movement of water
Plants mostly obtain water & minerals from soil.
Water moves up the xylem by bulk flow.
Movement of water depends on transpiration pull, cohesion & adhesion of water molecules, capillary forces, and strong cell walls.
Other mechanisms of water transport not as important:
Diffusion (note mosses, etc.)
Capillary forces (cohesions & adhesion)
Osmotic pressure (guttation)

47. Water – pushed or pulled?
Fig
Water – pushed or pulled?
Pushing of the xylem sap occurs via root pressure – root cells expend energy to pump mineral into the xylem. Minerals accumulate in the xylem sap lowering water potential there. Thus water flows into the xylem, generating a positive pressure that pushes fluid up the xylem.
Guttation – from root pressure

48. The availability of soil water and minerals
But root pressure can only push sap up a few meters and many plants generate no root pressure at all. How does water reach leaves of 100 m tall trees?
Xylem sap is pulled up the plant via transpirational pull. Leaves actually generate the negative pressure necessary to bring water to them.
The availability of soil water and minerals
Animation (animation~4) Mineral uptake in roots
Long-distance transport of water from roots to leaves

49. Translocation
The transport of food throughout a plant is known as translocation.
Sugar from mesophyll cells in the leaves and other sources must be loaded before it can be moved.
Often sieve tube members accumulate very high sucrose concentrations – 2 to 3 times higher than concentrations in the mesophyll – so phloem requires active transport using proton pumps
At the sink end of a sieve tube, the phloem unloads its sugar. Phloem unloading is a highly variable process; its mechanism depends upon the plant species and the type of organ. In any case, the concentration of sugar in the sink cells is lower than in the phloem because the sugar is either consumed or converted into insoluble polymers like starch.
Phloem moves at up to 1 m/hour – too fast to be by diffusion. So phloem also moves via bulk flow – pressure drives it.

50. 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
The Plant Body: Secondary Growth: The Vascular Cambium

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

52. 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

53. 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

54. Resources Plants in Motion: Movement of Water in Plants
Transport in Plants
Root Pressure
Water Transport in 3 Parts