Tissues in Plants and Animals Introduction
Every organism, whether its body is unicellular or multicellular, is capable of performing all vital functions such as respiration, ingestion, excretion and reproduction. In multicellular organisms, because of the increase in body size, it is difficult for each cell to efficiently cope with the vast variety of the physiological needs of the organism. So cells group together to perform definite functions.
A group of cells of the same type or of a mixed type having a common origin and performing similar functions are called tissues.
Plant Tissues
The plant body is made up of different kinds of tissues.
Permanent Tissues
These tissues are derived from meristematic tissues. They have lost the power of dividing, having attained their definite form and size. In their earlier stages the cells are more or less similar in structure but slowly they become specialized and form permanent tissues. They can be classified into simple and complex.
Sub Topics
Simple Tissues
Parenchyma
Nature
Occurrence
Function
Collenchyma
Nature
Occurrence
Function
Sclerenchyma
Nature
Occurrence
Function
Sclereids
Simple Tissues
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A simple tissue is made up of one type of cells forming a uniform mass. There are three types of simple tissues:
Parenchyma
Collenchyma
Sclerenchyma
Parenchyma
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Parenchyma
Nature
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Cells are isodiametric i.e. equally expanded on all sides.
They may be oval, round, polygonal or elongated.
Nucleus is present and hence living.
The cell walls are thin and made of cellulose.
Cytoplasm is dense with a single large vacuole.
Intercellular spaces may be present.
May contain chlorophyll. Parenchyma which contain chlorophyll are called chlorenchyma.
Occurrence
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Found in the cortex of root, ground tissue in stems and mesophyll of leaves.
Function
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Store and assimilate food
Give mechanical strength by maintaining turgidity
Prepare food if chlorophyll is present
Store waste products like tanin, gum, crystals and resins
