Class: Introduction to Plant Biology (Sophomore-level)
Teachable Unit: General Plant-Water Relations
Our students already understand:
- properties of water, adhesion, cohesion, osmosis
- plant anatomy
- basic cell structure
Our students have prepared for lecture by reading the
assigned textbook chapter about plant-water relations.
Learning goal:
Understand how water moves through plants
Learning outcomes:
1. Describe the pathway of water from soil to plant
to atmosphere
2. Explain the processes that move water through plants
3. Analyze the effects of changing abiotic factors on
water movement in plants
Have you ever wondered?
http://www.youtube.com/watch?v=w6f2BiFiXiM
Group work (that we are skipping):
Draw a diagram of a tree and indicate
the direction/path of the water flow through the tree.
- Call group representatives to draw their group
drawings on board.
- Elicit comments on differences
- Come to group conclusion: soil, plant, atmosphere
- Post the drawing
Group work:
Which of the following processes are involved in
getting water to the top of trees?
1.
2.
3.
4.
5.
Osmosis: Yes or No?
Diffusion: Yes or No?
Active transport: Yes or No?
Capillary action: Yes or No?
Cohesion-tension: Yes or No?
[make sure incorrect assumptions are corrected,
with more time a conversation about each]
On your handout, indicate where these processes occur
[Group reps post results - discussion ensues]
How do trees get water to their tops?
Video about evapotranspiration
You observe water droplets on the margin of
geranium leaves at 6 am but not at noon.
Using your knowledge of plant-water relations &
the information below, explain this phenomenon.
6 am
12 pm
Match plants A to D
with biomes 1 to 4
1.
C.
2.
A.
3.
B.
D.
4.
Have students fill out the diagram collectively
on single large diagram (doc-cam, big poster, etc)
Teaching Strategy #1: Go through the responses
with them. Does anyone disagree with certain
responses? For each process from roots to shoots,
segue to mini-lecture teaching slides. Let students
reevaluate their drawings.
Teaching Strategy #2: do mini-lecture and let students
reevaluate their drawings.
Mini-lecture on each of the processes
-their properties
-their limits in terms of movement
Osmosis: gets water from soil into roots
Diffusion: mainly occurs in leaf to atmosphere because
the atmosphere has very little water vapor.
Active transport: doesn’t occur
Capillary action: gets you less than 1 meter above soil
surface.
Cohesion-tension: is the major mover.
Group work: revise your labels and share upfront.
Which processes are the most important at each point?