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fossils

Fossil & Fossilization – importance , types and divisions PALEOBOTANY The study of fossils of plant life of the geologic past is called paleobotany. Paleobotany tells us the story of preserved vestiges of the plant life of the past. In simplified language paleobotany may be defined as a branch of botany which deals with the study of such plants which ...

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pteridophytes

Occurrence and evolution of Pteridophytes Pteridophyta is a group of ancient plants. They formed the dominant part of the earths during Palaeozoic and Mesozoic periods. Majority of Pteridophytes became extinct. They are preserved in the form of fossils or coal deposits. Only a few living Pteridophyta are left. General structure The vegetative plant body is a sporophyte in Pteridophytes. Sporophyte ...

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Photoperiodism

Photoperiodism Photoperiodism is the response of a plant to the relative length of light and dark periods to produce flower. The relative length of day and night to which a plant is exposed is called the photoeriod. Photoperiodism is a photobiological process – a process that involves absorption of light by a receptor (usually a pigment) that results in activation ...

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Psilopsida Botany-Leptosporangiate fern

PSILOPSIDA TYPE PSILOTUM Occurrence Psilotum is distributed in tropical and subtropical regions. It may grow as an epiphyte on the bark of trees. It also grows on soil where humus is abundantly available. General structure The plant body is sporophyte. The plant is a small shrub. The plant body is differentiated into rhizome and aerial branches. 1.  Rhizome: Rhizome is ...

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Theories of ascent of SAP

Here are following theories which explain the ascent of sap in plants: a) Root pressure (b) Capillarity (c) Vital theory and (d) Cohesion-tension theory. (a) ROOT PRESSURE The hydrostatic pressure generated in the root which forces the water upward in the stem is called root pressure. Root pressure forces the water up from below. But it is believed that root ...

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SEX DETERMINATION

SEX DETERMINATION The chromosomes which determine sex in the different organisms are called sex chromosomes. ‘Fhe term –sex– refers to the processes that enable species to exchange materials between homologous chromosomes. Ii causes recombination. Recombination is essential to their mechanism for reproduction. Work on inheritance of sex started after discovery of Menders ork in 1900. The discovery of sex chromosomes ...

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Epidermis

EPIDERMIS Epidermis forms the outermost layer of cells on the primary plant body. It is present over stem. roots, leaves, flowers and fruits. In most plant. epidermis is composed of single layer of cells. But two or several layers are also found in different plants. When it is composed of single layer, it is called hypodermis. When it is composed ...

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PARENCHYMA AND COLLENCHYMA TISSUES

The group of cells performing some collective function is called tissue. Tissues organize the body of plant for performing different function. Many types of tissues associate with each other to form tissue system. Vascular system is an example of tissue system. The tissues have following characteristics: Tissues are composed of many cells. These cells may be of one type or ...

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Water Absorption

WATER Absorption: of water*, root hairs: .[he absorption of \safer from the soil takes place tlitimigh the root hairs. Ihe root hairs are in contact with the wateriilms on the soil particles. ‘[here is a thin lining of cytoplasm inside the root hair. This cytoplasm encloses a large vacuole filled with cell sap. The Cytoplasm and cell sap of the ...

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Eucalyptus

Eucalyptus Description The leaves are leathery in texture, hang obliquely or vertically, and are studded with glands containing a fragrant volatile oil. The flowers in bud are covered with a cup-like membrane (whence the name of the genus, derived from the Greek eucalyptos well-covered), which is thrown off as a lid when the flower expands. The fruit is surrounded by a ...

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