1. Transpiration
Definition -
Explain how water is carried by the transpiration stream, including the structure of xylem vessels, transpiration pull, cohesion, adhesion and evaporation.

2. Xylem vessels have:
no cytoplasm
holes in the cell wall
this helps the flow of water
cohesion sticks water together
help it to be pulled upwards
adhesion to the xylem wall tends to pull water up the xylem vessel.
The main cause of water movement is the transpiration pull - caused by the evaporation of water in the leaves

3. State that guard cells can regulate transpiration by opening and closing stomata.
State that the plant hormone abscisic acid causes the closing of stomata.

5. Explain how the abiotic factors light, temperature, wind and humidity, affect the rate of transpiration in a typical terrestrial plant.

6. Transpiration pull is caused by:
water evaporating from the surface of the spongy mesophyll cells
Water vapour diffusing through the stomata & out of the leaf

8. Outline how the root system provides a large surface area for mineral ion and water uptake by means of branching and root hairs.
List ways in which mineral ions in the soil move to the root
There are three processes:
·diffusion of mineral ions,
·fungal hyphae (mutualism),
·mass flow of water in the soil carrying ions.