Anatomy of flowering plants

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ANATOMY OF  FLOWERING  PLANT

Anatomy: Anatomy is the study of internal structure of organisms. Plant    anatomy includes organisation and structure of tissues.
 Tissue: A group of similar cells along with 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. Meristems
Apical meristem
Intercalary meristem
Lateral meristem
  • Occurs at the tips of roots and
• Occurs between mature tissue
•Occurs in the mature
     Shoots

regions of roots and shoots
  • Primary meristem
• Primary meristem
• Secondary meristem
   • Increase the length of plant
• Capable of forming branch
•Appears later than pri-

   and flower
mary meristem and res-
ponsible for secondary growth
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.

Types of Permanent Tissue



Simple

        Complex
Parenchyma      Collenchyma Sclerenchyma          Xylem                Phloem
Parenchyma : Thin walled cells, with intercellular spaces, cell wall is made up of cellulose. It performs the function like photosynthesis, storage, secretion.
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.
The Tissue System :
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.


Vascular Bundles

             Radial bundles                Conjoint bundles                   



(Xylem and phloem occur          (Xylem and phloem are situated at on different radii)    the same radius of vascular bundle)
Open

Collateral bundles

Bicolateral bundles

Concentric bundles

        Closed
        (with cambium)          (without cambium)

Anatomy of  Root
Dicot Root

Monocot Root
1.
Cortex is comparatively narrow.
1.
Cortex is very wide.
2.
Endodermis is less thickened
2.
Endodermal cells are highly thickened

casparian stripes are more prominent.

Casparian strips are visible only in young roots.
3.
The xylem and phloem bundles
3.
Xylem and phloem are more than 6

 varies from 2 to 5.

(polyarch).
4.
Pith is absent or very small.
4.
Well developed pith is present.
5.
Secondary growth takes place with the help of vascular cambium and cork cambium
5.
Secondary growth is absent.

Anatomy of Stem
Dicot Stem

Monocot Stem
1.
The ground tissue is differentiated
1.
The ground tissue is made up of

into cortex, endodermis, pericy and pith.

similar cells.
2.
The vascular bundles are
2.
The vascular bundles are scat

arranged in a ring.

tered  throughout the ground tissue.
3.
Vascular bundles are open, without
3.
Vascular bundles are closed,

bundle sheath and wedge-shaped

surrounded by sclerenchymatous bundle

outline.

sheath, oval  or rounded in shape.
4.
The stem shows secondary growth  due to presence of cambium between xylem and phloem.
4.
Secondary growth is absent.
5.
Stomata have kidney-shaped
5.
Stomata have dumb bell-shaped guard

guard cells.

cells.

Secondary growth in dicot stem : 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 + interfascicularcambium.
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)
Cork (phellem)  - From outer cells
Cork Cambium
Sec. cortex (phelloderm) - From inner cells (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.

Anatomy of Leaf

Dorsiventral (Dicot) Leaf
Isobilateral (monocot) Leaf
1. Stomata are absent or less abundant on the
1. The stomata are equally distributed
upper side.
on both sides.
2. Mesophyll is differentiated into two
2. Mesophyll is undifferentitated.
Parts upper palisade parenchyma and lower spongy parenchyma.
3. Bundle sheath is single layered and formed
3. Bundle sheath may be single or
of colourless cells.
double layered.
4. Hypodermis of the mid-rib region is collen-
4. Hypodermis of the mid-rib region
chymatous.
is sclerenchymatous.


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