Notes of class 9

(ii) Plastid :- 

• Plastids are the cell organelles present in plant cell only.
• There are three kinds of plastids - Chloroplast ; Chromoplast and leucoplast.

(A) Chloroplast :- The chloroplast is surrounded by double membrane. Ground material of chloroplast is called stroma. In chloroplast coin like/disc like structure is present called thylakoid. Pile of thylakoid is called Granum ( plu. Grana ). One granum is attached with other granum by fret ( stromatal thylakoid ). In the sroma of chloroplast ribosome and DNA is present which make it semi autonomous cell organelle. Granum contain chlorophyll pigment in it . Main function of chloroplast is photosynthesis.

(B) Chromoplast :- Chromoplast is coloured plastid . It gives colour ( except green, voilet, blue, purple ) to flower fruit and other parts of plant. Example - Xanthophyll, carotene etc.

(C) Leucoplast :- The leucoplast is colourless plastid. Its main function is to store the food. There are three kinds of leucoplast on the basis of stored food in it :-

(a) Amyloplast :- Store starch in it.

(b) Proteinoplast :- Store protein in it.

(c) Elaioplast :- Store fat in it.