Short note on Functions of Nucleus, Endoplasmic Reticulum, Plastids and Golgi Complex
FUNCTIONS OF NUCLEUS:
(1) Nucleus and
Protoplasm of cell are responsible for various function of the cell. If they
are separated, both of them die. Nucleolus is controlling centre of vital
activities of the cell.
(2) Nucleus
takes direct part in reproduction. Two reproductive nuclei called gametes (egg
cell and male gamete) fuse together to give rise to oospore which grows into an
embryo.
(3) Nucleus
takes the initiative in cell division i.e. if is nucleus that divides first and
is followed by the division of the cell. This is how the cell multiply in
number and the plant body grows.
(4) Nucleus is
regarded as the bearer of the hereditary characters i.e. it is through the
media of two reproductive nuclei that the characteristics of parent plants are
transmitted to the offspring. It is to benoted that it is the DNA of the
nuclear reticulum that is the sole hereditary material of two reproductive
nuclei.
ENDOPLASMIC RETICULUM:
It is a network
of tube like structure distributed throughout the cytoplasm of the cell. Some
of these tubes are connected with the nuclear membrane and some with cell
membrane. They appear to be associated with enzyme formation, Protein
synthesis, storage and transport of metabolic products. They may also
contribute to the formation of the cell plate in nuclear division and of
nuclear membrane around the newly formed nuclei.
ER is complex
finely divided vascular system extending from nucleus throughout the cytoplasm
to the margin of the cell. It may even extend to the neighbouring cells.
Cavities of ER are surrounded by membraneas and are quite variable in shape and
size. It exists in two forms rough or granular form with closely spaced
granules ribosomes or cytoplasm side and smooth or a granular form.
PLASTIDS
Cytoplasm of
platn cell consists of discoidal, oval or spherical bodies called Plastids.
They are present in all plant except bacteria, fungi and blue green algae.
Plastids are living. They are formed a fresh but arise from minute pre existing
bodies called Protoplastids already present in embryonic cells. They multiply
in number by division. On the basis of colour plastids are of three types i.e.
Leucoplasts, chloroplasts and chromoplasts. One form of plastids can change in
to another as Leucoplasts. Change into chloroplasts when the former are exposed
to light for a prolonged period. Similarly chloroplasts change into leucoplasts
in the continued absence of light. Similar changes take place in chromoplasts.
In young tomato fruit the leucoplasts gradually change into chloroplasts which
finally turn into chromoplasts as the fruit ripens. Leucoplasts are white and
occur in storage cells of roots and underground stems. They convert sugar into
starch. Chloroplasts are green plastids bearing green pigment chlorophyll.
Chromoplasts are yellow, orange and red and are present in petals of flowers
are fruits.
GOLGI COMPLEX
It was
discovered by and named after Golgi (1898) from animal cells. Later Poger and
Buvat (1957) discovered it from plant cells. It is found in all kinds of cells.
It has a series of concentrically bent double membrane, which in reality are
flattened membrane bound sacs which are refered to as cisterane, saccules or
lamellar units. The individual vesicles are sometimes known as golgisomes or
dictyosomes. The cisternae form a system of branched tubules. It is suggested
that the golgi apparatus like nucleus envelope is also derived from Endoplasmic
reticulum. Function of Golgi bodies is concerned with the secretion of Proteins
and complex Polysaccharides. It is also supposed to be forming a part of cell
pate and the secondary walls.
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