Plant Tissues

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PLANT TISSUES ___________________________________________________________________________________

Cell divides and forms two cells, which repeatedly divide and many cells are produced. This is essential for the development and growth. The cell produced by cell division are alike (same) in the beginning, but to perform different functions, they vary structurally afterwards. Thus, there exists various groups of cells to perform particular function. These aggregated groups of cells are called tissues. Tissues are present in higher plants and multicellular animals. In unicellular organisms the original single cell performs all the vital function itself. But in multicellular organisms, different life functions are carried out by different groups of cell. There is distribution of the functions and this is called division of labour A group of cells, more or less alike in form, having same origin and performing a particular function is called a TISSUE.

Plant Tissue

Meristematic Tissue (Meristems)

Permanent Tissue

Meristematic Tissues (Meristems) They are situated at the tips of the actively growing regions of the plants such as shoot apex and root apex. The cells of this tissue continuously divide and add new cells in the plants. Characteristics  The cells are structurally alike(same)  They are spherical, oval or polygonal  There are no intercellular spaces  They possess abundant cytoplasm and prominent nuclei  The vacuoles are absent or if there they are small  They continuously divide and produce new cells

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Types of Meristematic Tissues

Meristematic Tissues

Apical Meristem

Intercalary Meristem

Lateral Meristem

Apical Meristem

Present at the growing tips of stems and roots and increases the length of stem and root

Intercalary Meristem

Present at the base of the leaves or internodes on twigs

Lateral Meristem

Present at the girth (thickness) of the stem or root

Permanent Tissues The new cells formed by the Meristems gradually enlarge, become fully differentiated and mature and lose their capacity of cell division and form permanent tissues to perform various functions.

Permanent Tissues

Simple

Complex

Parenchyma

Xylem

Collenchyma

Phloem

Sclerenchyma

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Simple Permanent Tissue Simple permanent tissues are made up of only one type of cells. Parenchyma Characteristics

       

Present in almost all the organs of plants Cells are spherical, oval, elliptical, polygonal or elongated Cells are isodiametric Cell wall is thin and made up of cellulose Cells are living and contain sufficient amount of cytoplasm in them Cells have intercellular spaces among them Cells possess large vacuoles in their cytoplasm Parenchyma containing chloroplasts with green pigment chlorophyll are called Chlorenchyma and perform the function of photosynthesis.

Functions

 Synthesize the food and store it  Store tannins, gums, resin and some inorganic substances  To fill spaces between different tissues and act as a supporting ground tissue. Collenchyma Characteristics

 Cells are spherical, oval, elliptical, polygonal or elongated  Cell wall is made up of cellulose and shows the deposition of pectin which is more prominent in the angular regions of the cell where they come in contact with each other.  Cells are living and contain sufficient amount of cytoplasm in them  Cells don’t have intercellular spaces among them Functions

 To provide mechanical strength  To render elasticity and flexibility. Sclerenchyma Characteristics

 Cells are long and fiber like and are called fiber cells. The cells are narrow and tapering at both the ends.  Cell wall is having the deposition of lignin.  Cells are dead and devoid of protoplasm (living substance of the cell)  Cells don’t have intercellular spaces among them 3

 Some special types of Sclerenchyma present in the hard seed coats and soft pulp of fruits are called stone cells or sclereids. Functions

 To provide mechanical strength and rigidity to the plant Complex Permanent Tissue Complex permanent tissues are made up of more than one types of cells and work as a single unit. Xylem The complex permanent tissue that conducts water and dissolved mineral salts upwards from root to leaves is called a Xylem. Xylem consists of tracheids (tubular structure), vessels (tubular structure), xylem parenchyma (stores food and helps in the sideways conduction of water) and xylem fibres (Supportive function). Characteristics

 Cells have thick walls  Cells are dead cells Functions

 Xylem conducts water and dissolved mineral salts upwards from toot to leaves and Phloem The components of phloem are sieve cells, sieve tubes, companion cells, phloem parenchyma and phloem sclerenchyma. Sieve tube is an important component of phloem and they are tubular cells with perforated walls. Characteristics

 Cells are living.  Cells contain cytoplasm. Functions

 Phloem is concerned with translocation of organic material to the various plant organs.

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