Notes

Transpiration - The loss of water from a plant's leaves: through evaporation
Transpiration Stream - The continuous movement of water through a plant
Transpiration:
1) Water enters root hair cells via osmosis
2) Water moves between cells through plasmodesmata
3) Water enters the xylem and moves to the stem and leaves
4) Water evaporates from the leaves through stomata
5) Evaporation produces a pressure gradient; water is pulled up through the xylem

Cohesion-Tension Theory:
Water molecules 'stick' to the xylem by adhesion
Water molecules stick to each other by cohesion


FACTORS THAT AFFECT THE RATE OF TRANSPIRATION
Light Intensity - Higher lite intensity, increase rate of photosynthesis, More open stomata
Temperature - Increased temperature, increased kinetic energy of water vapour molecules
Air Movement - Increased concentration gradient with more air movement (wind)
Humidity - Decreased humidity, increased concentration gradient


QUESTION 4 OF TRANSPIRATION STREAM WORK
ai) The stomata allows for Carbon Dioxide to be diffused for photosynthesis

aii) Guard cells

b) 25/5 = 5 (Upper) 85/5 = 17 (Lower)


c) The table of data shows that there are much more stomata on the lower side of the leaf than the upper side. This is due to the sunlight the upper side receives and to reduce water loss on the bottom.


d) When the water potential is high, guard cells take up the water by osmosis, this means the guard cells become turgid, causing the stomata to open. When there is insufficient water, cells lose water, leaving the cells as flaccid. The stomata close.