1. TRANSPORT IN PLANTS

2. Transport System
The vascular tissues found in plants are the xylem and the phloem
The function of the xylem is to transport water and mineral salts
The function of the phloem is to transport food materials: mainly sugars and amino acids

3. Where Are The Xylem And Pholem?
In the Leaf
mid-rib
vein
phloem
xylem

4. Where Are The Xylem And Pholem?
In the Stem
Phloem
Xylem
(note thickened cross walls)
Cross-section of stem
High magnification of a single vascular bundle

5. Transport Of Water And Mineral Salts
and is lost to the surroundings by the process called transpiration
is used in respiration and other cellular activities
transported up the stem by xylem vessels
Water is absorbed from surrounding soil by root hairs

6. Transport Of Water And Mineral Salts
The Uptake of Water
Up xylem vessels to plant
Water from soil
absorbed into root hair cell
across cortex cells
across phloem
into xylem vessels

7. Transport Of Water And Mineral Salts
The Uptake of Mineral Salts
Plants absorb mineral salts in the form of ions dissolved in soil water through the root hairs. This may take place via diffusion.
When there is a lower concentration of ions in the soil than the root hairs, ions do not diffuse into the root hairs.
It involves the movement of ions against a concentration gradient, and to do this root hairs need energy. This process is called active transport.

8. Transport Of Water And Mineral Salts
Adaptations of the Root Hair Cell
The root hair extends from the root cell. It is long and narrow. This provides a larger surface area to volume ratio for water and nutrients to be absorbed.
Soil particles
Water and mineral salts
The root hair cell is living. It carries out respiration to replace energy that is required for active transport.
The cell sap in the root hair cell is of lower water potential than the soil solution. This allows water to enter the root hair by osmosis.

9. Transport Of Water And Mineral Salts
Transport in the Xylem
There are 3 forces that move the water upwards in the xylem:
Root pressure - a force that pushes water up the xylem (produced by the continuous movement of water through the root cells.
Capillary action - a force that pushes water up the narrow xylem vessels.
Transpirational pull - a force that pulls water up the xylem (produced by evaporation of water from the leaves).

10. Transpiration Pull In Plants
Transpiration is the loss of water in the form of water vapour from the leaves, especially through the stomata, as a consequence of gaseous exchange
The importance of transpiration:
Transpiration pull which is a main factor in ‘lifting’ and sustaining the flow of water and mineral salts from roots up to the rest of the plant

11. Factors Affecting The Rate Of Transpiration
Transpiration is dependent on the opening of the stomata and the evaporation of water in the intracellular spaces of the leaf
This is affected by environmental conditions:
Humidity of the air – the more water vapour present in the surrounding air, the lower the rate of evaporation from the plant
Temperature – which also affects the rate of evaporation
Light – which stimulates the stomata to open
Wind speed – which transports water vapour away from the transpiring surface

12. Factors Affecting The Rate Of Transpiration
Wilting
cell surface membrane
cytoplasm
What happens during wilting?
Water escapes from the vacuole.
Turgor pressure decreases.
The cytoplasm shrinks and the cell membrane pulls away from the cell wall.
The cell loses its firmness and becomes soft. The plant becomes flaccid and limp. At this stage, cell is plasmolysed.

13. Translocation
The movement of sugars and amino acids via the phloem is called translocation
Glucose produced by photosynthesis in leaf is converted to sugars
(mainly sucrose) and translocated
to different parts
of the plant
To growing regions
to be used as energy for growth
If the plant requires more energy than can be produced, food stores are mobilised, converted back to sugars, and transported to wherever it is needed
Transport in the phloem occurs in both directions up and down the plant (bidirectional movement)
To storage organ (fruit)
to be stored mainly as sugars
To storage organ (tubers in roots)
To be stored mainly as starch