1. Transpiration
Water Uptake in Plants

2. Plants Need Water
Photosynthesis
Keep cells turgid

3. Easy For Moss

4. But taller plants must move water long distances

5. Transpiration! Evaporation of water from leaves
Creates a suction, or pull of water up the plant

6. Transpiration-Cohesion-Tension
There is a pull on the water
Water forms H- bonds with itself, and sides of walls
Like water through a straw

7. Cost-Benefit Analysis
Costs
Benefits
Plant can lose a lot of water and become dehydrated
Plant can get water to leaves for photosynthesis

8. Control Mechanism – Guard Cells
Open and close stomata/stoma (pores)
Allows plants to control gas/water exchange
Closed stomata conserve water, but no photosynthesis is possible

9. What Controls Stomata?
Circadian rhythm
Light
Dehydration

11. Stomata and Evolution Plants have evolved to have different amounts
Some have stomata only on underside of leaf, some on both, some only on top
Some open stomata at night only and fix carbon dioxide into an organic compound
Stomata open
Stomata closed

12. Factors that Can Affect Transpiration Rates
Temperature
Humidity
Sunlight
Presence of water
Wind
# and location of stomata
Leaf surface (waxiness)