What are plastids? How are they classified on the basis of the type of pigments? Name them and their pigments and mention their functions.
Plastids are double-membrane bound organelles of different shapes, that are found only in plant cells and contain pigments and storage products. They are of three types : (i) Leucoplasts These are the oval, spherical, rod-like or filamentous colourless plastids which are found in storage organs. Their main function is to store reserve materials like starch (amyloplasts), proteins (aleuroplasts) and fats (elaioplasts). (ii) Chromoplasts • These are coloured plastids containing mainly the yellow, red and orange pigments (carotene and xanthophyll). • These are found in petals of flowers and skin of fruits. • They attracts agents for pollination and dispersal of fruits/seeds. (iii) Chloroplasts • These are the green plastids containing mainly chlorophylls and very little carotene and xanthophyll. • Their main function is photosynthesis and the formation of starch.
