Respiratory Quotient (RQ)

About Respiratory Quotient (RQ)

RQ is measured by Ganong’s Respirometer.

(i) RQ for carbohydrates in aerobic respiration is unity. 

e.g., in germinating seeds of cereals, leaves, flowers and fruits.

RQ =

(ii) RQ for fats and proteins  in aerobic respiration is less than one.

In germinating fatty seed (Castor, sesame, lin seed etc.).

For RQ =

For Proteins RQ = 0.7 – 0.9

(iii) RQ for organic acids in aerobic respiration is more than one.

In fleshy plants (e.g., members of Cactaceae and Crussulaceae)

For Oxalic acid RQ =

For Malic acid RQ =

(iv) RQ for anaerobic respiration is infinity as oxygen is not used.

RQ =

(v) RQ for succulent plants at night is zero, as CO₂ is not evolved but fixed internally.

(vi) RQ for germinating seeds : 

For fatty seeds like castor, sunflower, cotton, RQ < 1

For other germinating seeds like that of wheat, maize, rice, RQ = 1