alternative pathways in photosynthesis. figure 10.20 a review of photosynthesis
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Alternative Pathways in Photosynthesis
Figure 10.20 A review of photosynthesis
“C3” Plants
Guard cells Pore Stoma
18 µm
Leaf surfaces contain stomata
Photosynthesis relies on CO2 entering the leaf and O2 leaving the leaf
Leaf cross-section
CO2
Carbon dioxide diffuses into leaves through stomata
H2O
BUT: water also escapes through
the stomata
CO2 stored in mesophyll cell
CO2 used inadjacent bundle sheath cell
Organicacid
Calvin cycle
CO2
G3P
CO2
C4 plants sequester CO2 in certain cells
C4 pathway
Examples of C4 plants: corn, sugarcane, many grasses
Figure 10.18 C4 leaf anatomy and the C4 pathway
C4 Plants
CO2 usedduring the day
CO2 storedat night
CO2
CO2
G3P
Calvincycle
Organicacid
CAM plants sequester CO2 at night
C4 pathway
Examples of CAM plants: pineapples, cacti, and most succulents.
CAM Plants
Welwitschia
Figure 10.19 C4 and CAM photosynthesis compared