Respiratory quotient is the ratio of volume of CO2 released to the volume of O2 taken in respiration. R.Q=VolumeofO2absorbedVolumeofCO2evolved R.Q. of carbohydrate = One R.Q. of fats and proteins = Less than one R.Q. of organic acids = More than one R.Q. of succulent plants = Zero R.Q. of anaerobic respiration = infinite.