Plants still carry out respiration in the day. Respiration is the process of oxidation of glucose to release energy for cell activities so that plants can survive. Hence, a plant still need to respire to have energy to carry out cell activities.
However, if you are talking about the plant taking in oxygen, then the plants do not actually have to take in oxygen during the day. This is so because the plant produces more than enough oxygen needed for respiration to occur when they photosynthesise in the day. That is also the reason why plants are able to release oxygen in the day. Some of the oxygen produced by photosynthesis is used by the plant itself while the rest is released into the atmosphere.
