These notes for CBSE Class 11 Biology cover Chapter 6: Anatomy of Flowering Plants. They define anatomy as the study of internal structure and tissues as groups of cells performing specific functions. Key concepts include meristematic tissues (capable of division) and permanent tissues (derived from meristems, unable to divide). The notes detail collenchyma (providing mechanical support) and sclerenchyma (composed of dead cells). Important vascular tissues like xylem (conducting water and minerals) and phloem (transporting food) are explained, including their components and types like protoxylem and metaxylem. The three tissue systems – epidermal, ground, and vascular – are outlined. Finally, the process of secondary growth in dicot stems and roots, involving vascular and cork cambium leading to increased girth, is discussed. These notes are ideal for revising the internal structure and organization of flowering plants.
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Anatomy : Anatomy is the study of internal structure of organisms. Plant
anatomy includes organisation and structure of tissues.
Tissue : A group of similar cells alongwith intercellular substance which
perform a specific function.
Meristematic tissues : The meristematic tissue is made up of the cells which
have the capability to divide. Meristems in plants are restricted to a specialised
regions and responsible to the growth of plants.
Axillary bud : The buds which are present in the axils of leaves and are
responsible for forming branches or flowers.
Permanent tissues : The permanent tissues are derived from meristematic
tissue and are composed of cells, which have lost the ability to divide.
Collenchyma : It is formed of living, closely packed isodimetric cells. It’s
cells are thickened at the corners due to deposition of cellulose and pectin. It
provides mechanic support to the growing parts of the plant.
Sclerenchyma : It is formed of dead cells with thick and lignified walls.
They have two types of cells : fibres and sclereids.
Xylem : Xylem consists of tracheids, vessels, xylem fibres and xylem parenchyma.
It conducts water and minerals from roots to other parts of plant.
Protoxylem : The first formed primary xylem elements.
Metaxylem : The later formed primary xylem.
Endarch : Protoxylem lies towards the centre and metaxylem towards the
periphery of the organ.
Phloem : Phloem consists of sieve tube elements, companion cells, phloem
fibres and phloem parenchyma. Phloem transports the food material from leaves
to various parts of the plant.
Protophloem : First formed phloem with narrow sieve tubes.
Metaxylem : Later formed phloem with bigger sieve tubes.
1. Epidermal tissue system : It includes cuticle, epidermis, epidermal hairs,
root hairs, trichomes and stomata.
2. The ground tissue system : It is made up of parenchyma, collenchyma,
sclerenchyma. In dicot stems and roots 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 and phloem.
An increase in the girth (diameter) in
plants. Vascular cambium and cork cambium (lateral meristems) are involved in
secondary growth.
1. Formation of cambial ring : Intrafascicular cambium + interfascicular
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)
(Phellogen + Phellem + Phelloderm) = Periderm
Secondary growth in dicot roots : Secondary growth in dicot root occurs
with the activity of secondary meristems (vascular cambium). This cambium is
produced in the stele and cortex, and results in increasing the girth of dicot roots.
Plant anatomy is the study of the internal structure of plants, including the organization and structure of their tissues.
Meristematic tissues are composed of cells that have the capability to divide and are responsible for plant growth in specific regions.
Xylem consists of tracheids, vessels, xylem fibres, and xylem parenchyma, and its primary function is to conduct water and minerals from the roots to other parts of the plant.
The three main tissue systems are the epidermal tissue system, the ground tissue system, and the vascular tissue system.
Secondary growth is an increase in the girth or diameter of plants, primarily involving the activity of lateral meristems like vascular cambium and cork cambium.
Periderm is a protective outer layer of tissue in woody plants, formed from the cork cambium, cork, and phelloderm.
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