Question

What is the disadvantage of photorespiration? Explain how the photorespiratory losses are overcome in plants like sugarcane.

Answer 1

Photorespiration is a process which involves loss of fixed carbon as $C{O}_2$ in plants in the presence of light.

Disadvantages of photorespiration: This process does not produce ATP or NADPH and is a wasteful process. Rather, it results in the release of $C{O}_2$ with the utilisation of ATP. It leads to a 25 percent loss of the fixed $C{O}_2$.

Sugarcane has developed a mechanism to overcome photorespiratory losses. Sugarcane is a $C_4$ plant. These plants have special leaf anatomy called Kranz anatomy. They have two types of cells i.e., mesophyll cells and bundle sheath cells, which are required for $C_4$ pathway. The particularly large cells around the vascular bundles of $C_4$ plants are called bundle sheath cells, these cells may form several layers around the vascular bundles, they are characterised by having a large number of dimorphic chloroplasts, grana are absent, thick walls impervious to gaseous exchange and no intercellular spaces. Due to this anatomy, photorespiration does not take place in $C_4$ plants. So, these plants show greater productivity and higher yield as compared to the $C_3$ plants.