Question

Recollect certain colours in plants. Name the plant and its part where the particular colour is found. What do you call the organelles which contain pigments?

Answer 1

Plastids are only present in the plants . They are known as kitchen of the cell. The internal organisation of the plastids consists of numerous membrane layers embedded in a material called the stroma. Plastids are similar to that of mitochondria in external structure. Like the mitochondria, plastids also have their own genetic material that is DNA and ribosomes.

Complete answer:
Plastids are found in all plant cells and in euglenoids etc. The plastids are easily observed under the microscope because of their size as they are large. Depending upon their colour and the pigments present in them .they are of three main types that are leucoplasts, chromoplasts and chloroplasts.

(A) Leucoplasts : They are colourless plastids which generally occur near the nucleus in non-green cells. They have variable size, form and stored nutrients, Granum is absent. There are three types of special leucoplasts . So they can form other plastids .

(B) Amyloplast :- They are starch-containing leucoplasts, e.g. potato tuber, rice etc. They do not form any other kind of plastid.

(C) Chloroplast :- They are greenish plastids which possess photosynthetic pigments, chlorophylls and carotenoids and take part in the synthesis of food. Majority of the chloroplasts of the green plants are found in the mesophyll cells of the leaves. They vary in size, shape and number and do not form other plastids.

(D) Chromoplast :- Chromoplasts are formed either from leucoplasts or chloroplasts. Change of colour from green to reddish during the ripening of tomato and chilli is due to transformation of chloroplasts to chromoplasts. The orange colour of carrot roots is due to chromoplasts

Note: There are three types of special leucoplasts
1)Amyloplast : They are starch-containing leucoplasts, e.g. potato tuber, rice etc.
2)Elaioplasts : They store fats and also store oils, e.g., castor.
3)Aleuroplast: These leucoplasts that are specialised to store proteins, e.g., aleurone cells of maize.