Which one of the following is wrong in relation to photorespiration : -
A
It occurs in chloroplasts
B
It occurs in daytime only
C
It is a characteristic of $C_4$ plants
D
It is a characteristic of $C_3$ plants
The answer is C.
Solution
Photorespiration occurs when RuBisCO uses $O_2$ instead of $CO_2$ (oxygenase activity), producing phosphoglycolate. It involves three organelles: chloroplasts, peroxisomes and mitochondria, and it starts in the chloroplast; true. It depends on light (it occurs only in the daytime, along with photosynthesis); true. It is a characteristic feature of $C_3$ plants, especially at high temperature and high $O_2$; true. In $C_4$ plants, the $C_4$ pathway concentrates $CO_2$ around RuBisCO in the bundle sheath cells, so its oxygenase activity is suppressed and photorespiration is negligible. So it is not a characteristic of $C_4$ plants. So the wrong statement is that photorespiration is a characteristic of $C_4$ plants.
ConceptPhotorespiration absent in C4 plants
Photorespiration in past papers
7 questions from this chapter have appeared across 6 exam years.