1. Water uptake, movement and loss

2. How plants take up water
The plant obtains water from the soil through the root hairs…
…which grow between soil particles…
…to absorb water in the pores between particles.

3. Root hairs

4. Diffusion
Water moves
from an area of higher concentration (the leaf air spaces)
to an area of lower concentration (the atmosphere)
Epidermis of the leaf
Higher concentration of water molecules in the leaf air spaces
Lower concentration of water molecules in the atmosphere
Water diffuses down the concentration gradient from higher to lower concentration

5. Epidermis of the root hair (selectively permeable membrane)
Osmosis
Water molecules move
from an area of relatively high concentration (the soil)
to an area of lower concentration (the root)
through a semi-permeable membrane (root cell walls)
Epidermis of the root hair (selectively permeable membrane)
Higher concentration of water molecules in the soil
Lower concentration of water molecules in the root
Water diffuses down the concentration gradient from higher to lower concentration

6. Osmosis at work
The pores in the membrane are too small to allow sugar to pass from the plant to the soil
Epidermis of the root hair (selectively permeable membrane)
Higher concentration of water molecules in the soil.
Lower concentration of water molecules in the root. Concentrated sugar solution.
Water diffuses down the concentration gradient from higher to lower concentration.
Sugar cannot diffuse through the membrane

7. Water uptake is influenced by:
The amount of moisture in the soil
The structure of the soil – larger particles allow more water movement and root penetration
The temperature of the soil – take up rates increase as temperature increases
The concentration of nutrients in the soil solution
How well the plant can take up the solution – most take-up occurs in the root hairs which grow from the youngest part of the root. Older parts are less permeable.

8. PHLOEM CELL
THEY CONDUCT FOOD FROM LEAVES TO REST OF PLANT
THEY ARE ACTIVE AT MATURITY AND TEND TO STAIN GREEN
PHLOEM CELL ARE FOUND OUTSIDE OF THE XYLEM
PLHLOEM CELLS CONTAIN COMPANION CELL AND SIEVE CELLS
COMPANION CELLS DISOLVE FOOD AS SUCROUSE THROUGH THE SIEVE CELLS

9. Translocation: how water moves in the plant
As xylem cells develop, the end walls between them break down to create long tubes inside the plant

10. 2. Water diffuses through cells 3. Water enters root xylem
Transpiration
How water taken in through root hairs enters the xylem
2. Water diffuses through cells
3. Water enters root xylem
1. Water enters root hair

12. Transpiration
Water molecules cling together in the narrow channels of the xylem
Evaporation of water from the leaves pulls adjacent water molecules to the leaf surface
Each water molecule pulls up the molecule below it – so the whole water column moves up the plant

13. Transpiration: how plants lose water
Stoma
1. Water reaches leaf xylem vessels
2. Water diffuses through leaf cells
3. Water vapour diffuses through stoma

14. Stomatal opening
Blue light is detected by phototrophin and switches on the pumps
Chloroplasts supply ATP to power them
Potassium is pumped in.
Water flows in and the stomata open.

15. The rate of transpiration
Transpiration increases in relation to higher levels of:
Dry air
Temperature
Wind
Atmospheric pressure
Water supply
All factors which remove water molecules faster and increase the gradient from high to low amounts. Try this with different leaves.