Question

What is the common value of PQ (photosynthetic quotient) of a leaf?
A. $>1$
B. $<1$
C. One
D. Zero

Answer 1

Hint: Photosynthesis is carried out by all green plants. Photosynthetic quotient (PQ) is the ratio of the amount of carbon dioxide absorbed to the amount of oxygen evolved.

Complete answer: Photosynthesis is a process by which all green plants, some bacteria, and some autotrophs convert light energy of the sun into chemical energy and simultaneously produce glucose from carbon dioxide and water.
Oxygen is released out as a by-product of this process. The photosynthesis process can be divided into two-phase: light-phase and dark-phase.
Thylakoids of the chloroplast are the major site for the light-phase.
The dark-phase reactions occur in the chloroplast stroma.
A French chemist Boussingault made a significant contribution in the field of plant physiology, which is the discovery of the definition of the photosynthetic quotient (PQ).
It is the ratio of the amount of carbon dioxide absorbed to the amount of oxygen evolved.
In a leaf, the amount of $CO_2$ absorbed and amount $O_2$ of evolved are equal; hence the value PQ is one.

So, the correct option is C. One

Note: PQ measures the efficiency of a plant because it is an index of the photosynthetic activity of a plant relative to its respiratory activities.
The oxygen evolution may be done by a cell or any organism capable of photosynthesis.