i did not understand why CO 2 concentration is more of a limiting factor for C 3 plants. ??
In C3 plants,the primary acceptor of CO2 is RUBP. This reaction is catalyzed by enzyme known as RUBisCO. RuBisCO is the most abundant enzyme & is characterized by the fact that its active site can bind to both CO2 and O2. The relative concentration of O2 and CO2 determines that which of the two will bind to the enzyme. If the concentration of CO2 decreases, then O2 binds to RuBisCO. As a result,the RUBP instead of being converted to 2 molecules of PGA, binds with O2 to form one molecule of PGA and phosphoglycolate, This process is known as photo respiration. Hence, in order to bind with enzyme RuBisCO, CO2 should be present in higher concentration.