Cell The Unit of Life — BIOLOGY STD 11 Science — Question

Plastids are small organelles. They contain food pigments and are found in the cytoplasm of the cell of plant.
They can be both region specific (occur according to their function) or species specific.
There are three types of plastids:
Chromoplasts, Chloroplasts and Leucoplasts. 

1. Leucoplasts: Leucoplasts are found near the nucleus and are colorless in nature. They have lamella whereas Grana and photosynthetic pigments are absent. They occur majorly in non green plants. 
   
2. Chromoplasts: Chromoplast is found to be reddish or yellow in colour. This is because of the fact that they contain carotenoid pigment. The fascinating colours of many flowers are because of this pigment or plastid.
   
3. Chloroplast: Chloroplast is green in colour.
   

They occur in mesophyll cells which are photosynthetic. They also take part in food synthesis.
Apart from being region specific, plastids are also species specific. For example, Chloroplasts that are there in Euglenoids have three layers present.