CH-6 (ANATOMY OF FLOWERING PLANTS) BIOLOGY CLASS -XI, CBSE NCERT EXAM NOTES

Chapter-6
Anatomy of Flowering Plants

Points to Remember

Anatomy : Anatomy is the study of internal structure of organisms. plant anatomy includes orgnisation and structure pf tissues.
Tissue is a gruop is cells having a common origin and usually performing a common function.
There are two types of tissues (i) Meristematic (ii) Permanent
Meristematic tissues :The meristematic tissue tissue is made up of the cells whicb have the capability to divide. Meristems in plants are restricted to specialised regions and responsible to the growth of plants.

Axillary bud : The buds which are present in the axils of leaves (Consist of cells left behind from shoot apical meristem) and are restricted for farming branches of flowers.

Permanent tissues : The Permanent tissues are derived from meristematic tissue, are composed pf cells, which have lost the ability to divide and have become structurally and functionally specialised.

Parenchyma : Living, thin walled isodiametic cells, with interceullar spaces, cell wall is made up of cellulose. It performs the functions like photosynthesis, storage, secretion.

Collenchyma : It is formed of living, closely packed cells. Its cells are thicknened at the corners due to depositon of cellulose and pectin. It provide mechanical support to the growing parts of the plant. It is either found in homogenous layer or patches.

Sclerenchyma : It is formend of dead cells with thick and lignified walls. Provide mechanical support to organs. Theybhave two types of cells: fibres and sclerids.
(a) Fibers- are thick walled, elongated and pointed cells.
(b) Sclereids- are spherical, oval or cylindrical, highly thicknened dead cells with narrow lumen. Found in walls of nut, pulp pf fruits like guava, seed coat of legumes anf leaves of tea.

Xylem : Xylem cosists pf trachedis vessels, xylem fibres and xylem parechyma. It conducts water and minierals from roots to other parts and plant.
(a) Trachedis Tube like cells with thick lignified walls amd tapering ends; dead, without protoplasm.
(b) Vessel Long cylindrical structure made up of many cells with large central cavity, devoid of protoplasm present in angiosperms.
(c) Xylem fibres Highly thicknened walls; with obliterated lumens; septate or aseptate.
(d) Xylem Parenchyma Living amd thin walled; cell walls made up cellulose, store food material in form of strach or fat.


Readial conduction of water takes place by ray parenchymatous cells


Protoxylem : The first formed primary xylem elements.
Metaxylem : The later formed primary xylem.
Endrach : Protoxylem lies towards the center and metaxylem towards the periphery of the organ; in stem.
Exarch : Protoxylem toward periphery and metaxylem towards center; in roots.
Phloem : Phloem consist of sieve tube elements, companion cells, phloem fibres and phloem parenchyma; Phloem transports the food mayerial from.leaves to various parts of the plant.

(a) Sieve tube elements :
• Long tube like structures arranged logitudinally.
• Associated with companion cells.
• End walls are perforated to form sieve plates.
• Functiona of sieve tubes are controlled by the nucleus of companion cells.

(b) Companion Cells
• Specialised parenchymatous cells assocated with sieve tube elements
• Connected with sieve tube elementa by pit fields present between their common longitudinal walls.
• Help to maintain pressure gradientnin sieve tubes.

(c) Phloem Parenchyma
• Made up of elongated, tapering cylindrical cella with dense cytoplasm and nucleus.
• Cell wall made of cellulose with pits through which plasmodealsmatal connections exist between cells.
• Store food material.

(d) Phloem fibres (bast fibres)
• Are sclerenchatous; absent in primary phloem but present in secondary phloem.
• Elongated, unbranched pointed, needle like apices with thick cell walls.
  


Protophloem : First formed phloem with narrow sieve tubes.


Metaphloem : Later formed phloem with bigger sieve tubes.

The Tissue System :

1. Epidermal Tissue System : It includes cuticle, epidermis, epidermal hairs, root hairs, trichomes and stomata.

(a) Cuticle : Waxy thick layer outside epidermis, prevents the loss of water.
(b) Epidermix : Outer most layer of primary plant body.
(c) Epidermal hair : Help in absobing water and mineral from soil.
(d) Trichomes : Help in preventing water loss due to transpiration.
(e) Stomata : Regulate process of transpiration and gaseous exchange.


Somatal apparatus : The stomatal aperture, guard cells and surrounding subsidiary cells are together celled stomatal apparatus.

2. The Ground Tissue System : It is made up of parenchyma, Collenchyma, sclerenchatous, In dicot stems and roots (both monocots and dicots) the ground tissue is divided into hypodermis, cortex, endodermis, pericycle, medullary rays and pith.

3. The Vascular Tissue System : It includes vascular bundles which are made up of xylem an pholem.

Anatomy of Root

Casparian Strips : The tangential as well as radial walls of endodermal cells of dicot roots have depositon of water impermeable, waxy material, suberin in the form of casparian strips.

Anatomy of Stem

Secondary Growth Dicot Stem : An increase in the girth (diameter) in plants, vascular cambium and cork combium (lateral meristem) are involved in secondary growth.

1. Formation of cambial ring : Intrafascicular cambium + interfasicular cambium.
2. Formation of secondary xylem and secondary phloem from cambial ring.
3. Formation of spring wood and autumn wood.
4. Development of cork cambium (phellogen)

Secondary Growth in Dicot Roots : Secondary growth in dicot roots occur with the activity of secondary meristems ( vascular cambium ). This cambium is produced in the stele and cortext, and results in increasing the girth of dicot roots

Anatomy of Leaf - 1



Spring Wood and Autumn Wood



Heartwood and Sapwood

Lenticels : Produced when phellogen cuts off parechyma cells on outer side. These cells rupture the epidermis forming lens shaped opening called lenticels.

Function : Permit exchange of gases.

Bulliform Cells : Large, empty, colourless adaxial cells with vein in leaves which maintain turgidity of leaves.