Essential Idea:
Structure and function are
correlated 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
Applications:
- Adaptations of plants in deserts and in saline soils for water conservation
- Models of water transport in xylem using simple apparatus including blotting or filter paper, porous pots and capillary tubing
Skills:
- Drawing the structure of primary xylem vessels in sections of stems based on microscope images
- Measurement of transpiration rates using potometers
- Design of an experiment to test hypotheses about the effect of temperature or humidity on transpiration rates