TYPES OF PLASTIDS

(1) LEUCOPLASTS

These are present in ground parts of plants, internal parts of herbaceous stems and deep tissues of plants where sun light is not available.

Devoid of pigments and internal lamellar structures.

On the basis of function of leucoplast i.e. food storage, they are divided into three types - (i) Amyloplasts - Leucoplast storing starch.

(ii) Aleuroplasts - Leucoplast storing Proteins.

(iii) Elaioplasts - Leucoplast storing Oil, droplets and fats.

(2) CHROMOPLASTS

These are coloured plastid, responsible for colour of flowers, fruits and algae.

In algae brown colour due to phaeoplast and red colour due to rhodoplast. Phaeoplast contains pheucoxanthine and rhodoplast contains phycoerythrine.

Chromoplast contain different types of pigments (carotenes, Xanthophylls etc) Chlorophylls either absent or occur in very less amount.

Chromoplasts occurs mainly in pericarp and petals. In flowers chromoplast helps in pollination and in fruits these plastids help in dispersion of seeds because different colour attracts insects and birds.

Red colour of red chillies and red tomatoes is due to a red pigment of chromoplasts, "Lycopene". Lycopene is a type of carotene. Yellowish - orange colours of fruits are due to a-carotene, b-carotene and g-carotene. b-carotene is precursor of vitamin-A. Richest source of b- carotene are carrot roots.

Choromoplasts also occur in petals but colours of petals are mainly due to water soluble pigments which occur in cell sap. e.g. Anthocyanin - Blue or violet or red pigment; Anthoclor pigment responsible for yellow colour.

(3) CHLOROPLASTS

Schimper (1883) coined the term chloroplastid for green plastids.

Mayer called them Autoplast. Chloroplast name proposed by Erera.