Q.Respiratory quotient is zero in succulent plants. Why ?

The Respiratory Quotient (RQ), or respiratory ratio, is the ratio of the volume of CO2 released to the volume of O2 consumed during respiration, and its value indicates both whether respiration is aerobic or anaerobic and which respiratory substrate is being used. For complete aerobic oxidation of carbohydrate, RQ = 1 (unity), since $CO_2$ released equals $O_2$ consumed. For anaerobic breakdown of carbohydrate (e.g. alcoholic fermentation), RQ is infinite, since CO2 is released with no O2 consumed. In succulents such as Opuntia and Bryophyllum, where carbohydrate is only partially oxidised to an organic acid (malic acid) with O2 consumed but no CO2 released, RQ = 0. For proteins and fats, RQ is less than unity (e.g. tripalmitin gives RQ = 102/145 = 0.7) because these substrates are …