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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.
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