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

Respiratory Quotient (R.Q.) = volume of CO2 evolved ÷ volume of O2 consumed. Carbohydrates give R.Q. = 1, fats/proteins give R.Q. < 1, while organic-acid substrates give R.Q. > 1.

When a respiratory substrate is oxidised, the ratio of CO2 released to O2 consumed depends on how oxidised the substrate already is:

1. Carbohydrates (glucose, fructose): oxidation is perfectly balanced, so R.Q. = 1.
2. Fats: contain proportionally less oxygen relative to carbon and hydrogen, so extra O2 is needed for complete oxidation, making R.Q. < 1 (about 0.7). …

Correct answer: (c) 0.9

The Respiratory Quotient (RQ = CO2 released / O2 consumed) for protein respiration is approximately 0.9.

The Respiratory Quotient (RQ) is the ratio of the volume of CO2 released to the volume of O2 consumed during respiration of a particular respiratory substrate. For carbohydrates, which are fully oxidised, RQ = 1.0. For fats, which contain relatively less oxygen per carbon and require more O2 for complete oxidation, RQ is lower, about 0.7. Proteins, being intermediate in oxygen content …