1. Plant Organs Stems: Structure & Function Transport in Plants1
Structure, Functions & Adaptations

2. Stems: Types Herbaceous Woody Growth
Die at the end of a growing season (annuals)
Grow larger every growing season (Trees and shrubs)
Colour
Green
Bark
Example
Ferns & grass
Oak, Maple, & Pine

3. Stems: function
1. Support - for leaves and reproductive structures (more support is offered by woody stems than by herbaceous)
2. Transport - vascular system (xylem & phloem) 3

4. Structure of stems

5. Internal structures Vascular Tissue Cambium - between xylem & phloem
- forms the rings in trees
- divides to form secondary xylem & phloem
Epidermis
- outer covering
- single layer in herbaceous stems
- multi-layered in woody stems
Pith & Cortex
- made of parenchyma tissue

6. Do you know?
Tree rings are made from the growth of secondary xylem (Cambium)!

7. Vascular Tissue Xylem Hollow Vessels (like straws) Joined end to end
End walls are perforated
Secondary xylem is thickened with LIGNIN

8. Vascular Tissue Phloem
Hollow tubes connected end to end with perforations at the end (sieve tubes)
Companion cells carry out life functions to maintain both types of cells

9. Transport Structures Leaf Stem Root Xylem Phloem Xylem Xylem Phloem

11. Root
Stem
Leaves 11

12. Early Transport (mosses)
NO VASCULAR SYSTEM
PASSIVE TRANSPORT: when particles move down the concentration gradient (High - Low)
DIFFUSION: movement of particles from an area of high concentration to an area of lower concentration
OSMOSIS: the movement of water molecules across a membrane 12

13. How water gets in the Roots?
- Roots have a higher concentration of nutrients than the water outside the root
- Water moves into the root (down the concentration gradient)

14. How Water Moves UP Against Gravity
1 - Pushing water up
* Root pressure
2 - Pulling water up
* Transpiration, cohesion, adhesion

15. Pushing water UP - Root Pressure
Once water moves into the root cortex pressure is exerted on the fluid in the xylem and pushes it upward
Some water moves from the cortex into the xylem
More water is absorbed by the root hairs 15

16. Root Pressure

17. Pulling Water UP (Cohesion-Tension Model)
A. Transpiration - water evaporation from leaves
~ 100 L / day
- exerts tension on the water attached in the xylem tubes
C. Adhesion - water molecules stick to the xylem walls
B. Cohesion - force of attraction between water molecules

19. A variety of physical processes are involved in the different types of transport
TRANSPIRATION, the loss of water
from leaves, creates a force within
leaves that pulls xylem sap upward. 3
CO2 O2
Light
H2O
Sugar
Sugars are produced by
photosynthesis in the leaves.
Source to Sink explains how it is
carried DOWN the phloem 4
COHESION and ADHESION work to carry water molecules up from the roots to the leaves. 2
OSMOSIS - Roots absorb water
and dissolved minerals
from the soil. 1 O2
H2O
CO2
Minerals
Figure (page 563)

20. Transport of Sugar through Phloem
Photosynthesis in the leaves produces GLUCOSE
Translocation is the process of transporting glucose to all other parts of the plant, through the phloem
Source to Sink
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