Why does calvin pathway take place in bundle sheath cells in c4 cycle and not in mesophyll cells as in c3 cycle????
The C4 plants adopt a different pathway for photosynthesis than normal due to high temperatures and Oxygen concentration in the atmosphere.
The reason behind an alternate path is to prevent oxidation of Ribulose biphosphate sugar by the enzyme RUBISCO ( RibUlose BIphoSphate Carboxylase Oxygenase) as it acts as an oxidising agent in high O2 concentration and low CO2 concentration.
Therefore, at high temperatures and Oxygen concentration in the atmosphere the plants do not perform normal photosynthesis and try to increase the concentration of CO2 by storing and concentrating CO2 in the mesophyll cells.
The mesophyll cells are present in the upper layers of the leaf exposed to the effect of O2 concentration . Therefore, they do not perform photosynthesis as in C3and rather store CO2 to increase its concentration to prevent oxidation of food.
The CO2 is stored in the form of malic acid which is then transported to Bundle sheath cells.The Bundle sheath cells are present internally around the vascular tissue. Since, they are located inside and not exposed to atmospheric O2 and rather increased concentration of CO2 liberated by Malic acid. In the presence of CO2 these cells perform normal photosynthesis by C3 pathway, as the RUBISCO enzyme acts as carboxylase in the presence of high CO2 concentration.
The reason behind an alternate path is to prevent oxidation of Ribulose biphosphate sugar by the enzyme RUBISCO ( RibUlose BIphoSphate Carboxylase Oxygenase) as it acts as an oxidising agent in high O2 concentration and low CO2 concentration.
Therefore, at high temperatures and Oxygen concentration in the atmosphere the plants do not perform normal photosynthesis and try to increase the concentration of CO2 by storing and concentrating CO2 in the mesophyll cells.
The mesophyll cells are present in the upper layers of the leaf exposed to the effect of O2 concentration . Therefore, they do not perform photosynthesis as in C3and rather store CO2 to increase its concentration to prevent oxidation of food.
The CO2 is stored in the form of malic acid which is then transported to Bundle sheath cells.The Bundle sheath cells are present internally around the vascular tissue. Since, they are located inside and not exposed to atmospheric O2 and rather increased concentration of CO2 liberated by Malic acid. In the presence of CO2 these cells perform normal photosynthesis by C3 pathway, as the RUBISCO enzyme acts as carboxylase in the presence of high CO2 concentration.