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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