Plastids are divided into three types based on the pigment content. These are-
- Leucoplast : Greek word Leuco means colorless. Colorless plastids are called leucoplasts. In presence of light it can transform into chromoplast or chloroplast. It can be semicircular, rectangular or cylindrical in shape. Leucoplasts are found in plant roots, lower stems, seeds, dividing tissues, gametes etc. Polytoma algae contain leucoplasts. There are three types of leucoplasts. These are-
(i) Amyloplast : The leucoplasts that store starchy food are called amyloplasts. Amyloplasts are present in plants like rice, wheat, potato, bhutra, barley, cown etc.
(ii) Elioplast: The leucoplasts that store fatty food are called elaioplasts. Plants like mustard, coconut, Chinese almond, soybean, linseed etc. contain elaioplast.
(iii) Aleuroplast: All leucoplasts that store protein food are called aleuroplast or proteinoplast. Chickpeas, peas, kesari and lentils contain aleuroplasts.
- Chloroplast: Greek word Chloros means green. Green colored plastids are called chloroplasts.
- Chromoplast : Greek word Chroma means colored. Plastids of color other than green are called chromoplasts. It is colored due to carotene and xanthophyll. Chromoplasts probably evolved from chloroplasts. Flower petals, colored fruits and seeds, and carrots contain chromoplasts. Insects are attracted to the colors of flowers and leaves and help in pollination. Different types of chromoplasts are-
(i) Carotenoplast: The orange colored chromoplast is called carotenoplast. Monica Sánchez flowers, bignonia flowers and carrots contain carotenoids.
(ii) Rhodoplast : Red colored chromoplast is called rhodoplast. Rhodoplasts are present in spp.
(iii) Pheoplast: Yellow-brown colored chromoplast is called pheoplast. Diatoms and brown algae contain pheoplasts.
(iv) Xanthoplast: Yellow colored chromoplast is called xanthoplast. Dandelion flower, sunflower flower, golden flower, ginger flower, marigold flower, ripe fruit skin contain xanthoplast.