(1) Chromoplasts :-In chromoplasts fat soluble carotenoid pigments like carotene, xanthophyllas and others are present. This gives yellow, orange or red colour to the part of the plant. Chlorophylls either absent or occur in very less amount. Chromoplasts occurs mainly in pericarp and petals. Eed colour of tomatoes is due to the red pigment "Lycopene" of chromoplasts,.

`->` Chromoplasts also occurs in petals but red to blue color range in petals is mainly due to water soluble pigments

Anthocyanin occur in cell sap.

(2) Chloroplasts:-The chloroplasts contain chlorophyll and carotenoid pigments which are responsible for trapping light energy essential for photosynthesis.

(3) Leucoplasts :-The leucoplasts are the colourless plasiids of varied shapes and sizes with stored nutrients: Amyloplasts store carbohydrates (starch), e.g., potato; elaioplasts store oils and fats whereas the aleuroplasts store proteins. Pigments and lamellar structure absents in Leucoplasts. Cenerally occurs in non green and underground plant cells.

`->` All types of plastids have common origin from proplastids, sac like non-lamellar structures.

`->` Different types of plastids may transform from one form to another. Because genetic meteral is similar. But chromoplasts never transform to chloroplasts.

`->` Majority of the chloroplasts of the green plants are found in the mesophyll cells of the leaves.

`->` Number varies from 1 per cell of the Chlamydomonas a green al~p to 2040 per cell in the mesophyll.

`->` These are lens-shaped, oval, spherical, discoid, or even ribbon shaped.

`->` Length and width are also variable.

Length `= 5- 10 mu`m
Width `= 2-4 mu`m

Membrane: Like mitochondria the chloroplast are also double membrane bound. Out of the two, the inner

membrane is relative less permeble. (Outer membane contain porins)

The space limited by the inner membrane is called the stroma (matrix)

(a) Thylakoids :

`->` In the stroma a number of organised flatted mernbranous sacs are present called thylakoids.

`->` Thylakoids are arranged in stacks like the piles of coins called grana (singular : granum) or the intragranal thylakoids.

`->` Each chloroplast contains about `20-100` granum.

`->` Stroma lamellae are flat membranous tubules (Fret channel or Stroma thylakoids) connecting the thylakoids of the different granum.

`->` The membrane of the thylokoids enclose a space called lumen.

`->` Chlorophyll (photosynthtic pigments) are present in the thylakoids membrane.

`->` A photosynthesis functional unit (l.ocated in thylakoids membrane) contains of about `250` to `400` molecules of various pigments (Chl�a, Chl-b, Carotenes, Xanthophylls etc.) is called as Quantasomes.

`->` The stroma of the chloroplast contains er:Jzymes required for the synthesis c:if carbohydrate e.g. glucose

(i.e. enzymes of Calvin cycle or Dark reaction) and protein synthesis.

`->` The important enzyme of calvin cycle is Eubisco.

`->` B.ubisco is the most abundant enzyme on the earth.

`->` Rubisco forms `16%` proteins of the chloroplast

`->` Stroma contain small double-stranded circular DNA molecules .

`->` Chloroplast have more genes as compared to mitochondria (l 00 or more genes)

`->` The stroma of chloroplast contain `70`s Eibosome. (Chlororibosonw)

`->` The Ribosome of the chloroplast are smaller (`70`s) than the cytoplasmic ribosomes (`80`s)

Chloroplasts have thier own genetic system & complete protein synthesis machinery (ds - DNA, HNA, Hibosome, Enzymes, Amino acids) thus chloroplasts are also called as semi autonomous organelle of the cell.

(1) Photosynthesis: The chloroplasts trap the light energy of sun and transform it into the chemical energy in the form
glucose.

(2) Balancing of `O_2` & `CO_2` in nature.

(3) Chloroplasts participate in cytoplasmic inheritance.

(4) Chloroplasts impart the pleasing greenary to the earth.

(5) Chloroplasts store vitamin K, E, Rubisco protein and Fe etc.

(1) From Proplastid

(2) From binary fission of pre-existing plastids.

ORIGIN: Endosymbiotic origin by a cyanobacterium