1. Transport in Living Things
Chapter 25
Chapter 25.5 Transport System in Flowering Plants

2. What did we learn? Transport system of plants Water roots osmosis
Consists of
Phloem
Xylem
Is a living tissue made up of sieve tubes and companion cells
Is a continuous hollow tube with lignified walls
enters
Water
Transports food substances
roots
Transports water and mineral salts
via
osmosis

3. Lesson Objectives At the end of the lesson, You should be able to:
relate the structure and functions of root hairs to their surface area, and to water and ion uptake
state that transpiration is the loss of water vapour from the stomata
define the term translocation as the transport of food in the phloem tissue
identify the positions of xylem vessels and phloem in sections of a typical dicotyledonous stem and leaf, under the light microscope, and state their functions
relate the structure and functions of root hairs to their surface area, and to water and ion uptake
state that transpiration is the loss of water vapour from the stomata

4. Transport of mineral salts

5. Plant Profile What process is being used to take in mineral salts?
Name: Claudia
Owner: Farmer A
Characteristics: Is watered and fertilizer is added everyday. 5

6. Transport of mineral salts
Plasma membrane of root hair cell
Sap in root hair
Soil solution
Mineral concentration low
Mineral concentration high
Mineral salts
Diffusion

7. Plant Profile What process is being used to take in mineral salts?
Name: Lydia
Owner: No one
Characteristics: No one takes care of it and the soil is dry and mineral- poor. 7

8. Transport of mineral salts
Qn: Can the root hair absorb ions if the concentration is higher in the root hair sap compared to the soil solution?
Yes!!!
Plasma membrane of root hair cell
Sap in root hair
Soil solution
Mineral concentration high
Mineral concentration low
Mineral salts?
Active transport

9. Translocation
Definition: It is the transport of manufactured food substances such as sugars and amino acids in plants. How can we show that the phloem carries materials from the leaves to other parts of the plant?

10. “Ringing” experiment Take the branch of a woody plant
Remove a ring of bark from around the main stem.
Put it into water
Observe it over a few weeks

11. “Ringing” experiment
Region with bark removed
Unringed twig
Water A B

12. After a few weeks…
The part of the stem just above the cut region will swell

13. Transpiration
Definition of transpiration: The loss of water vapour from the aerial parts of the plant, especially through the stomata of the leaves
Just as in our original example of water potential, the water moves from the intercellular spaces to the atmosphere. Water is lost from cells to the intercellular spaces, and these cells then being at a lower (more negative) water potential than their neighbours will abstract water from them. This continues across the leaf until it reaches the bundle sheath cells. These abstract water from the xylem. Water is highly cohesive. The water molecules are bonded to each other by hydrogen bonds, and are thus very cohesive. Experiments to demonstrate the cohesive strength of water have generally put the strength of bonding of water molecules at several hundred atmospheres. (This only works in the absence of contaminating gasses which will come out of solution under vacuum, hence columns of water do get broken in the plant under normal physiological conditions). The entire column of water therefore is dragged up, and the reduction in pressure potential in roots literally sucks water in. Again this is propagated across the pith of the root up to the endodermis.

14. Similarity? Functions of transpiration:
Cool the plant; prevent scorching
Facilitates the lifting of water and mineral salts from roots to leaves

16. Transpiration pull
Leaf cells lose water
concentrated cell sap = lower water potential
Evaporation of water from leaves
Draw water from cells deeper inside the leaf by osmosis
Cells remove water from xylem vessels
Creates a transpiration pull
The evaporation of water from leaves result in a suction force which pulls water up the xylem vessels
Suction force due to transpiration is transpiration pull

17. Factors affecting transpiration rate
Humidity of air
Temperature of air
Strong wind
Light
Size and shape of leaves (surface area)

18. Summary Food substances Water Mineral salts roots roots leaf
via
enters
Water
roots
via
Mineral salts
enters
roots
Food substances
Diffuses out of
Travels from
leaf
Leaves or aerial parts of the plant to
Other parts of the plant
via
Osmosis
Diffusion
Active
transport
via
Is the transport of manufactured food substances such as sugars and amino acids in the plants
Transpiration
Is the loss of water vapour from the aerial parts of the plant
Translocation