simple tissue.pptx

All about simple tissue.

1. SIMPLE TISSUES or SIMPLE PERMANENT TISSUES: Types & Functions PARENCHYMA COLLENCHYMA SCLERENCHYMA

2. SIMPLE PERMANENT TISSUE: A tissue is said to be simple when it is made of only one type of cell. The cells posses fix shape, size and function (Structurally and functionally same ) Normally have lost the power of division but sometime may regains power of division. Various simple tissue found in plant cells are: Parenchyma Collenchyma Sclerenchyma

3. PARENCHYMA: Also known as fundamental or ground tissue and present in almost all the parts of the body (cortex, pith , pericyle ,mesophyll of leaves, pulp of fruit, endosperm, etc ). Do not lose their protoplasm during maturation hence are living ( parenchyamtous cells) Are isodiametric and may be oval, rounded ,polygonal or elongated. The parenchyma are further divided into : Chlorenchyma (chloroplast e.g. leaves) Aerenchyma ( large air spaces e.g. Hydrilla , Nymphea ) Prosenschyma (thick walled, elongated e.g. pericyle of some plants) Storage parenchyma ( endosperm of seeds) Stellate parenchyma ( star like with short long arms e.g Petioles of banana)

4. FUNCTION OF PARENCHYMA Photosynthesis: Parenchyma cells chloroplasts help in photosynthesis ( Chlorenchyma ) Storage of food : They store water and food materials like starch grains and proteins in the cortex and pith of stems and roots. Provides buoyancy for the hydrophytes to float in water ( Aerenchyma ). Are turgid ( fully expanded cell) and give rigidity and maintain the shape of the plant body. Parenchyma cells with intercellular space allow the exchange of gases involved in the process of photosynthesis and transpiration. Gives rise to secondary meristem in the form of cork cambium and vascular cambium. They perform all vital activities of plants.

5. COLLENCHYMA: Contain protoplasm and are elastic , living and may be oval, rounded or polygonal in shape. The cell wall show thickenings at corner due to deposition of pectin (45%), hemicellulose (35%) and cellulose (20%) and provides mechanical support but never lignified. Are compact and intercellular spaces may or may not present. Usually occur in the hypodermis of dicot stems (Helianthus) and leaves. Generally absent in monocots and in roots. The collenchyma are further divided on the basis of thickening : Angular C ( deposition at angles e.g. Tomato, Tagetus ) Lacunate C (deposition on the walls of intercellular spaces e.g. Cucrubita stem) Lamellar or Plate C (deposition in the tangential walls of cells of Helanthus )

6. FUNCTION OF COLLENCHYMA The cell walls or Collenchyma are elastic and extensible and so it is an effective mechanical tissue Chief supporting tissue in young dicot stem and petiole of leaf and resist bending of stem. Present at the margins of some leaves and resists tearing effect of the wind. If chloroplast are present collenchyma cells help in photosynthesis.

7. SCLERENCHYMA: Sclerenchyma (Greek, sclerous = Hard) are thick walled, without protoplast and are dead at maturity but there are some sclerotic parenchyma Cells have hard lignified secondary walls (lignin deposition) and are rigid and impermeable to water. Sclerenchyma cells are of two types ( Fibers and Sclereids ). Sclerenchyma Fibers: Sclerenchyma fibers are elongated cells with pointed ends and are spindle shaped. They vary greatly in size (2-550 mm) Mostly occur in groups in hypodermis and in secondary xylem (wood fibers/xylem fibers) & phloem (phloem fibers). The cells have thick lignified secondary wall and the lumen is very much reduced and in certain areas the walls remain less thickened and are known as pits. On the basis of position present in plant they may be i. Surface fibers (over the surface of plant organs, coconut) ii. Wood fibers (secondary xylem and may be further of two types libriform fibres and fibre tracheids ) iii. Bast fibers (in pericyle , cannabis; phloem, Hibiscus ( extraxylary fibres )

8. Sclerieds are called stone cells because of their thick wall and hard wall . On the basis of the shape sclerieds are classified into five types. Brachysclereids : These sclerieds are short and more or less isodiametric . It is found in the fruits like pear. Macrosclereids : These are elongated and rod-like. It occurs in the seed coats of beans Osteosclereids or Bone cells: The sclereids are bone or barrel shaped. This is found in the seed coats of pisum . Astrosclereids: They are also known as star cells. They are star shaped. They are found in petioles and leaves. e.g Nymphaea Tricchosclereids : These are much elongated and hair-like sclereids . Sometime they are branched. They occur in the leaves of olea.