Transport in the xylem of plants
​Understandings:
• Transpiration is the inevitable consequence of gas exchange in the leaf.
• Plants transport water from the roots to the leaves to replace losses from transpiration.
• The cohesive property of water and the structure of the xylem vessels allow transport under tension.
• The adhesive property of water and evaporation generate tension forces in leaf cell walls.
• Active uptake of mineral ions in the roots causes absorption of water by osmosis

Application: Adaptations of plants in deserts and in saline soils for water conservation.

Skill: Drawing the structure of primary xylem vessels in sections of stems based on microscope images

Application: Models of water transport in xylem using simple apparatus including blotting or filter paper, porous pots and capillary tubing

Transpiration
Skill: Measurement of transpiration rates using potometers. (Practical 7)
Skill: Design of an experiment to test hypotheses about the effect of temperature or humidity on transpiration rates.