Plastids - Introduction, Classification & Functions

Plastids - Introduction:

Plastids are membrane bound organelle found in all plant cells and some protists (euglina). Dr Ernst Haeckel discovered plastid.

Plastid Classification:

Plastids are classified into two types, they are:

1. Leucoplast
2. Chromoplast

Plastid Classification

Leucoplasts:

• These are colourless plastids (non pigmented).

• Leucoplasts do not have grana.

• Leucoplasts are found in Roots, Rhizomes, Tubers, etc. ,parts of the plants which are not exposed to sunlight. 

• Main function of Leucoplasts are storage of food.

Based on their function Leucoplasts are further classified into 3 Types:

a. Amyloplasts - Stores carbohydrates. Location: Potato Tuber, Wheat, Rice, etc

b. Allueronplasts - They are also known as proteoplasts. They stores aluerone protein. Location: Maize, Pulses.

c. Elaioplasts - Stores Fat. These can be found in castor seed, ground nut, etc.

Chromoplasts:

• These are coloured plastids (Colored due to presence of Pigments).

• Chromoplasts have grana / Thylakoid

• Chromoplasts are found in Leaf, Petals, Fruits, etc. , parts of the plants exposed to sunlight.

• Main function of chromoplasts are photosynthesis, attraction of pollinating agents.

Chromoplasts are further classified based on the type of pigment present:

a. Chloroplasts - Green Pigmented plastid, found in Green leaves, green stem,etc

b. Pheoplast - contains Xantophyll & Fucoxanthin. These are found in brown algae.

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c. Rhodoplast - contains red pigment called to phycoerythrin. these are found in red algae.

Some of the other pigments present in plants are:

1. Lycopin - Red pigment found in Tomato.

2. Capsanthin - Red pigment found in Red Pepper.

3. Carotenes - Orange / Red pigment found in carrots.

Leucoplasts and Chromoplasts are interchangable, means that when lecuoplasts attains pigments it becomes chromoplasts and when the chromoplasts lose pigments it can become leucoplasts.