Question

Compare and contrast CAM and C4 photosynthetic pathways. Discuss evolutionary factors that led to the emergence of PEPcarboxylase.

Answer 1

Characteristics	C4 photosynthesis	CAM photosynthesis
1. Kranz Anatomy	Presesnt	Absent
2.CO2:ATP:NADPH ratio	1:5:2	1:6.5:2
3.Carboxylating Enzyme	In Mesophyll-PEP carboxylase In bundle sheath-RuBP Carboxylase	In dark--PEP carboxylase In light-RuBP carboxylase
4. Initial CO2 acceptor	PEP	PEP
5.First stable product	oxaloacetate	oxaloacetate
6. optimum temperature for photosynthesis	30-40 degree celcius	>40 degree cecius
7. CO2 compensation point(ppm)	0-10	0-5 in dark
8.Photorespiration	Not easly detectable	Detectatble in afterno9.on
9.Calvin cycle operative	Along with Hatch and Slack cycle	long with Hatch and Slack cycle

PEP Carboxylase is present in both C4 and CAM plant. it can fix the carbon at very low concentrataion of hydrogen carbonate in comparision RuBisCo. Due to PEP carboxylase plant can suvive in extreme environmet like heat and lack of water.