Why does Oxygen bind with rubisco in photo-respiration?

the enzyme rubisco can use either CO2 or O2 as a substrate. Rubisco adds whichever molecule it binds to a five-carbon compound called ribulose-1,5-bisphosphate (RuBP). The reaction that uses CO2 is the first step of the Calvin cycle and leads to the production of sugar. The reaction that uses O2 is the first step of the photorespiration pathway, which wastes energy and "undoes" the work of the Calvin cycle

When a plant has its stomata open, CO2 diffuses in, O2 and water vapor diffuse out, and photorespiration is minimized. However, when a plant closes its stomata O2 from photosynthesis builds up inside the leaf. Under these conditions, photorespiration increases due to the higher ratio of O2 to CO2

In addition, Rubisco has a higher affinity for O2 when temperatures increase.