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Plant tissues, 9 cbse

Tissues are groups of similar cells that perform the same function and originate from the same source. There are two main types of tissues: plant tissues and animal tissues. Plant tissues include meristematic tissue and permanent tissue. Meristematic tissue is responsible for plant growth, as the cells continuously divide and later specialize. There are three types of meristematic tissue: apical meristem at shoot and root tips, intercalary meristem between permanent tissues, and lateral meristem under bark. Permanent tissue develops from meristematic tissue. There are two types - simple tissues with uniform cell type, and complex tissues with multiple cell types. The three simple tissues are parenchyma, collen

CHAPTER – 6 TISSUES
DEFINITION A group or collection of similar cells performing or help to perform same function and arise from the same origin are called tissues. The tissues are of different types depending on the functions of the organism, they are mainly of two categories PLANT TISSUES and ANIMAL TISSUES.
PLANT TISSUES Plants perform functions which are different from animals and also their structure is different , hence they have tissues which are different from animals. They are further classified into many sub categories which is shown in the table below:
MERISTEMATIC TISSUE • The main characteristic of this tissue is that it is responsible for the growth of plants. • The cells of this tissue continuously divide and later differentiate ( i.e. get converted ) into permanent tissue.
Characteristics of the cells/ tissue • The cells are made of thin & elastic cell wall made of cellulose. • The cells may be round , oval, polygonal or rectangular in shape. • They are compact, having no intercellular space. • There is a large nucleus and abundant cytoplasm. • The protoplasm contains very few or no vacuoles at all.
This tissue occurs at specific regions of the plant body • This is so because in plant body growth occurs only at these regions. • Hence , on the basis of this there are 3 types of meristem : 1. APICAL MERISTEM 2. INTERCALARY MERISTEM 3. LATERAL MERISTEM
APICAL MERISTEM As the name suggests this tissue is present at the apex of the main & lateral shoots and roots. This tissue gives the plant body a linear growth.
LATERAL MERISTEM This tissue lies on the sides of the plant body. It lies under the bark of the plant in form of cork cambium. It gives the plant it’s width or girth.
INTERCALARY MERISTEM This tissue is present at the base of the nodes, internodes, leaves etc. They are also present in between the permanent tissue. They give the plant growth in length.
PERMANENT TTISSUE • These tissues arise from the meristematic tissue. • The cells of this tissue gradually loose their power to divide and acquire a definite shape, size and function. • These tissues may be living or dead. • There are 2 types of permanent tissues 1. Simple permanent tissue 2. Complex permanent tissue.
SIMPLE PERMANENT TISSUE • This tissue comprises of same type of cells which perform the same function and all arise from the same origin. There are three categories of simple permanent tissues: Parenchyma, Collenchyma, & Sclerenchyma.
THE THREE SIMPLE PERMANENT TISSUES
PARENCHYMA • Characteristics: a) The cells are living. b) The cells are thin walled. c) There may or may not be intercellular spaces. d) They are the most unspecialized cells. e) No depositions are seen, the cell wall consists only of cellulose. f) There is a prominent nucleus, cytoplasm & vacuoles.
• There are some special types of parenchyma tissues : • Storage parenchyma : The cells enlarge to store nutrients & water. • Aerenchyma : Air cavities are present in the parenchyma tissue to provide buoyancy to the aquatic plants. • Chlorenchyma : These parenchyma cells have presence of chlorophyll & hence can perform the function of photosynthesis. Parenchyma tissue is found generally in all parts of the plant body. It forms the Ground tissue in leaves, stem, roots & fruits etc.
Functions of parenchyma : a) To store materials such as starch, proteins, hormones etc and waste products such as gum, tannin, resin etc. b) Parenchyma cells perform the metabolic activities of the plant. c) Forms the packaging tissue between the specialized tissue. d) By providing turgidity , they provide mechanical strength. e) Chlorenchyma helps in performing photosynthesis.
COLLENCHYMA
• Characteristics: • Functions : a) It has cells which are a) Providing mechanical somewhat elongated. strength is the primary b) The cell walls are thin function. except at the angular b) Provide flexibility. region ( where the cells c) Photosynthesis, as they join). The thickenings are contain chlorophyll. caused due to deposition of cellulose or pectin. They are present below c) There is o or less the epidermis in dicot intercellular space. stems and leaves. They d) The cells are living, have absent in dicot roots distinct nucleus & dense and all parts of protoplasm. monocot plants. e) They often contain chlorophyll.
SCLERENCHYMA