Question

In Botany class, teacher explains, Synthesis of one glucose requires 30 ATPs in C₄ plants and only 18 ATPs in C₃ plants. The same teacher explains C₄ plants are more advantageous than C₃ plants. Can you identify the reason for this contradiction?

Answer 1

C₄ Plants are more advantageous than C₃ plants because of the following reasons:

C4 Plants	C3 Plants
CO2 fixation occurs in mesophyll cells only.	CO2 fixation occurs in mesophyll and bundle sheath cells.
RUBP is the only CO2 acceptor.	PEPA Phosphoenol pyruvate in mesophyll is the acceptor in the first phase.
Fixation of CO2 occurs if the atmospheric concentration of CO2 is 50 ppm only.	It can fix carbon dioxide even if the atmospheric concentration of CO2 is below 10 ppm.
The optimum temperature is 20° to 25°C.	The optimum temperature is 30° to 45°C and is thus effective in tropical regions.
RUBP carboxylase enzyme also functions as oxygenase if the O, concentration is higher than carbon dioxide.	PEP carboxylase enzyme functions even at low carbon -dioxide concentrations.
Higher rate of photorespiration and hence rate of photosynthesis is reduced.	A minimal rate of photorespiration is seen is C4 plants.