2.54 describe the role of xylem in transporting water and mineral ions from the roots to other parts of the plant

Xylem: 
-transport water and mineral salts from roots up to shoots to leaves in transpiration stream.
*transpiration: evaporation of water from surface of plant
 
Features:
-no cytoplasm so is impermeable to water
-tough walls containing lignin (wood)
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The main thing to understand for 2.53 and 2.54 is that plants have 2 transport systems:
-Xylem carries water and minerals from roots to leaves in transpiration stream.
-Phloem performs translocation and sieve tubes move sugars, (sucrose and amino acids) from where they're produced to areas around the plant.
 
COMMON EXAM QUESTIONS:
1. How does water enter the root from soil? 
-Water molecules can only enter root hair cells by osmosis. 

2. How do mineral ions enter the root from soil?
-Minerals enter root hair cells from soil via active transport.

3. What are the features of xylem vessels?
-no cytoplasm, no nucleus
-end walls of these cells break down to provide a continuous unbroken column of water all the way up the plant.  The cell walls of xylem vessels made with protein lignin.

4. What causes water to move up the xylem?
-heat energy from the sun transpires water in the leaves and provides energy for this movement. (transpiration)
-water molecules are cohesive; they have a hydrogen bond between each other. This allows them to pull on each other up the xylem vessel.