Concept 2:
Analyzing the Processes of
Photosynthesis
PART 2 – Adaptations to Dry Climates
 Refer to pg 83-92 in Holtzclaw, Ch 10 in Campbell and
media resources
 Refer to pg 297-299 in Holtzclaw, Lab Inv 5 in Lab Manual
Try This!
 Which experiment will
produce 18O2?
A.
Exp 1
B.
Exp 2
C.
Both!
D.
Neither!
Try This!
 Which experiment will
produce 18O2?
A.
Exp 1
B.
Exp 2
C.
Both!
D.
Neither!
Do you know?
(Chapter 10)
 The summary equation of photosynthesis including the source
and fate of reactants and products
 How the leaf and chloroplast anatomy relates to photosynthesis
 How photosystems convert solar energy to chemical energy
 How linear electron flow in the light reactions results in the
formation of ATP, NADPH, and O2
 How chemiosmosis generates ATP in the light reactions
 How the Calvin cycle uses the energy molecules of the light
reactions to produce G3P
AP Investigation 5
You must know:
 How to determine the rate of photosynthesis and then be
able to design a controlled experiment to test the effect
of some variable factor on photosynthesis
NOW…
 Adaptations to hot, arid climates…
 CAM plants and C4 plants
Pineapple – CAM plant
Sugarcane – C4 plant
Hot, Dry Climates
 What’s the big deal?
 Stomata – water loss
 Rubisco – photorespiration
Stomata…
Stomata…
 Water exits via stomata during
transpiration (evaporation of
water through the stomata
- which pulls water up the plant
from the roots)
 If it’s a hot, dry day, plants need
to minimize water loss!
 Solution?
 Close/minimize stomata
 BUT? Lowers CO2 intake…
Rubisco…
 Remember rubisco?
 It’s the enzyme that fixes CO2 in the Calvin cycle of C3 plants
 The thing is… rubisco will also bind O2 in absence of CO2
 Causes breakdown of Calvin Cycle products…
Photorespiration
 Solution?
 Adapt!
Try This!
 The presence of only Photosystem I, not Photosystem II, in
the bundle sheath cells of C4 plants has an effect on O2
concentration. What is that effect, and how might that
benefit the plant?
Try This!
 The presence of only Photosystem I, not Photosystem II, in
the bundle sheath cells of C4 plants has an effect on O2
concentration. What is that effect, and how might that
benefit the plant?
 Without PS II, no O2 is generated in the bundle-sheath cells!
 This avoids the problem of O2 competing with CO2 for
binding to rubisco
 No photorespiration
Now…
 Practice
 Try Holtzclaw questions
 Go over Comparison Charts
 Try animation activities (Campbell Online)
 Re-Read about CAM plants and C4 plants and do worksheet
 P. Holtzclaw
 P. 200-202 Campbell
 Activity: Photosynthesis in Dry Climates (Campbell Online)
 Get Ready for Lab Investigation 5
 What factors affect the rate of photosynthesis in living leaves?