Nitrogen is not a constituent of

Answer: Option D

Nitrogen is not a constituent of the Idioblast.
An idioblast is an isolated plant cell that differs from neighboring tissues. They have various functions such as storage of reserves, excretory materials, pigments and minerals.
There are a variety of crystal types and shapes that can be stored within an idioblast. The most common substance for crystals is calcium oxalate, a common product of calcium abundance in plants.