1. Plant Structures Roots, Stems, and Leaves
Chapter 23

2. 23-1 Specialized Tissues in Plants
Plants are as successful if not more successful than animals
Seed plants have three main structures:
Roots
Stems
Leaves
Linked together by various means

3. 23-1 Specialized Tissues in Plants
Roots
Absorbs water and nutrients
Anchor plant to the ground
Hold soil in place and prevent erosion
Protect from soil bacteria
Transport water and nutrients
Provide upright support

4. 23-1 Specialized Tissues in Plants
Stems
Support for the plant body
Carries nutrients throughout plant
Defense system to protect against predators and infection
Few millimeters to 100 meters

5. 23-1 Specialized Tissues in Plants
Leaves
Main photosynthetic systems
Suseptable to extreme drying
Sight of oxygen/carbon dioxide intake and release

6. 23-1 Specialized Tissues in Plants
Plant tissue systems
Exist within the root, stems, and leaves
Dermal tissue
Vascular tissue
Ground tissue

7. 23-1 Specialized Tissues in Plants
Dermal Tissue
Outer covering
Single layer of cells
Cuticle – waxy coating
Trichomes – Spiny projections on the leaf
Roots have dermal tissue
Root hairs
Guard Cells

8. 23-1 Specialized Tissues in Plants
Vascular Tissue
Transport System
Subsystems
Xylem
Phloem
Subsystems are used to carry fluids throughout plant

9. 23-1 Specialized Tissues in Plants
Xylem
Two types
Seed plants
Angiosperms
Tracheid – long narrow cells
Walls are connected to neighboring cells
Will eventually die
Vessel Element – wider that trachieds

10. 23-1 Specialized Tissues in Plants
Phloem
Sieve Tube Elements
Cells arranged end to end
Pump sugars and other foods
Companion Cells
Surround sieve tube elements
Support phloem cells

11. 23-1 Specialized Tissues in Plants
Ground Tissue
Cells between dermal and vascular tissue
Parenchyma
Thin cell walls, large vacuoules
Collenchyma
Strong, flexible cell walls
Sclerenchyma
Extremely thick, rigid cell walls

12. 23-1 Specialized Tissues in Plants
Plant Growth
Meristems – tissues responsible for growth
Undifferentiated cells
Apical Meristem
Produce growth increased length
Differentiation
Cells will assume roles in the plant
Flower Development
Starts in the meristem

13. 23-2 Roots Types of Roots Taproots Fibrous roots Found in dicots
Long, thick root
Hickory and oak trees
Fibrous roots
Found in monocots
No single root larger than any other
Many thin roots

14. 23-2 Roots Root Structure Key role in water/mineral transport
Outside layer
Epidermis
Root hairs
Cortex
Central cylinder – vascular system
Root Cap – cellular production
Key role in water/mineral transport

15. 23-2 Roots
Root Functions
Anchor plant
Absorb water
Absorb nutrients

16. 23-2 Roots Plant Nutrient Uptake Plant requirements
Soil type determines plant type
Plant requirements
Oxygen, CO2
Nitrogen
Phosphorus
Postassium
Magnesium
Calcium
Trace elements

17. 23-2 Roots Active Transport in Plants Vascular Cylinder Root Pressure
Root hairs use ATP
Pump minerals from soil
Causes water molecules to follow by osmosis
Vascular Cylinder
Casparian Strip – water retention
Root Pressure
Forces water up into the plant

18. 23-3 Stems Stem Structure Essential part of transport system
Produce leaves, branches, and flowers
Hold leaves up
Transport substance between roots and leaves
Essential part of transport system
Function in storage and photosynthesis

19. 23-3 Stems Xylem and phloem – major tubule systems
Transport water and nutrients
Composed of three tissue layers
Contain nodes – attachment for leaves
Internodes – regions between the nodes
Buds – undeveloped tissue

20. 23-3 Stems
Stem Types
Monocot – vascular bundles are scattered throughout
Distinct epidermis
Dicot – vascular tissue arranged in a cylinder
Pith – parenchyma cells inside the ring

21. 23-3 Stems
Stem Growth
Primary growth – new cells produced at the root tips and shoots
Increases the length
Secondary growth – increase in stem width
Vascular cambium – produces tissue and increases thickness
Cork cambium – produces outer covering of stems

22. 23-3 Stems Formation of Vascular Cambium
Xylem and phloem bundles present intially
Secondary growth initiates production of a thin layer
The vascular cambium divides
Produces new xylem and phloem

23. 23-3 Stems Formation of wood Wood – layers of exlem
Produced year after year
Results from the older xylem not conducting water – heartwood
Becomes darker with age
Sapwood – surrounds heartwood

24. 23-3 Roots Formation of Bark
All the tissues outside the vascular cambium
Consists of outermost layers of dead cork
Water proof

25. 23-4 Leaves Main sight of photosynthesis Consist of:
Blade – thin flattened section
Petiole – stalk that attaches stem to blade
Covered by epidermis and cuticle
Create water proof barrier

26. 23-4 Leaves Leaf Functions Photosynthesis – occurs in the mesophyll
Palisade mesophyll – absorb light
Spongy mesophyll – beneath palisede level
Stomata – pores in the underside of the leaf
Guard Cells – Surround the stomata

27. 23-4 Leaves Transpiration Loss of water through its leaves
Replaced by water drawn into the leaf

28. 23-4 Leaves Gas Exchange Take in CO2 and release O2
Can also do the opposite – How?
Gas exchange takes place at the stomata
Not open all the time
Stomata is controlled by water pressure in guard cells

29. 23-5 Transport in Plants Water Transport
Active transport and root pressure
Cause water to move from soil to roots
Capillary action
Combined with active transport and root pressure, moves materials throughout the plant

30. 23-5 Transport in Plants Capillary Transport
Capillary transport results from both cohesive and adhesive forces
Water molecules attracted to one another
Water is also attracted to the xylem tubes in the plant
Causes water to move from roots to the stem and upward

31. 23-5 Transport in Plants Transpiration
Evaporation is the major moving force
As water is lost, osmotic pressure moves water out of vascular tissue
This pulls water up from the stem to the leaves
Affected by heat, humidity, and wind

32. 23-5 Transport in Plants Controlling Transpiration
Open the stomata – increase water loss
Close the stomata – decrease water loss

33. 23-5 Transport in Plants Transpiration and Wilting
Osmotic pressure – keeps plants semi-rigid
Wilting is a result of high transpiration rates
Loss of water causes a drop in osmotic pressure
Loss of rigidity
Conserves water

34. 23-5 Transport in Plants Nutrient Transport Source to Sink
Most nutrients are pushed through plant
Nutrient movement takes place in phloem
Source to Sink
Source – any cell that produces sugars
Sink – any cell where sugars are used
Pressure-flow Hypothesis