Fairly minor correction, but photosynthesis is essentially the opposite of cellular respiration. Plants do respirate and release CO2, but their photosynthesis more than offsets their respiration.
Late reply, respiration occurs in cells when they burn ATP energy, consuming Oxygen and producing Carbon Dioxide. Photosynthesis creates ATP rather than burn it. Plants will respirate and burn that ATP after it is created, but photosynthesis itself is not respiration. Hope you find this interesting!