PLASTIDS

By asghar khan lecturer in BotanyGovt: Degree College Totakan

PLASTIDS

are membrane bounded, mostly pigment containing bodies present in plants cells only

They are not found in fungal or animal cells Plastids are classified into three types i) Chloroplast ii) Chromoplasts iii ) Leucoplasts

Types of plastids

CHLOROPLAST

Large ,green, round or oval cytoplasmic organelle Contain green pigments called chlorophyll Chlorophyll is a complex organic compound

containing central Mg atom resembles hemoglobin Present in all photosynthetic eukaryotes Most obvious in leaf cells Vary in size from 4 um to 6um in diameter Number may be from one to one hundred per cell

STRUCTURE OF CHLOROPLAST

A chloroplast consist of three components i ) an outer most covering (envelop) ii ) Grana iii) Stroma

Outermost covering is formed of double membrane structure encloses the grana and stroma

Grana (singular granum meaning seed)

Grana (singular granum meaning seed)

Consists of many flattened fluid filled sacs called thylakoids

Many thylakoides grouped together forming a stacks or pile of coins called Granum

The grana are interconnected by layer called inter grana

Photosynthetic pigments are present within the membranes of the thylakoides

Light reaction of photosynthesis are taking place within the membranes of thlakoids of granum.

STRUCTURE OF CHLOROPLAST

Stroma Stroma is a large central space within the chloroplast

surrounded by double membrane envelope Home to grana,site of dark reaction of photosynthesis Covers most of the volume of chloroplast Contain enzymes, some ribosome's and small Circular

DNA in gel like solution called matrix Fix Carbon dioxide to manufacture sugar

CHLOROPLAST

CHROMOPLAST

CHROMOPLAST They Lack chlorophyll and are other than green may be red, orange or yellow in colour Mostly present in ripened fruits, petals of flowers and

autumn leaves They help in pollination and seed dispersal LEUCOPLAST These are colorless plastids, triangular or tubular in shape Present in underground food storage parts such as potato

tubers, radish root. Concerned with storage of food

FUNCTION OF PLASTIDS

Chloroplast absorbs light energy and store it in chemical form (ATP),all living organism use this chemical energy for their functions

Chloroplasts are involved in phtosynthesis,besides synthesis of food material oxygen is formed as a by product

Chromoplast present in petals & ripened fruits are involved in dispersal of seeds & also attract insects for pollination

Leucoplast are concerned with the storage of food in underground parts