Plant AnatomyAlso known as Micromprphology

of plants and plant- or vegetable-histology, is

concerned with the microscopic structure of the tissues, cells and organs of

plants.

Plant tissuesA tissue is a group of coherent cells

having similar form and function and have common origin.

Tissues are classified according to stage of development to:

Meristematic tissue: the cells have the ability of division.

Mature (permanent): the cells lost the power of division .

Meristematic tissueThey characterized by:

1 -Thin walled. 2- Isodiametric.3 -With dense cytoplasm.4 -With large nucleus.5 -Have proplastides.6 -No intercellular spaces.7 -No vacuole or presence of minute

ones.8 -No reserve food materials.

Classification of meristems

Apical meristems: located at the growing points of stems and roots e.g. those

present in stem and root apices.Intercalary meristems: present between two

permanent zone, present at base of internodes e.g. sugarcane and maize.

Lateral meristems: present laterally and cause increase in diameter of plant.

Different types of mature tissues

1 -Parenchyma2- Collenchyma3 -Sclerenchyma4- Epidermis5 -Endodermis6- Pericycle7 -Cork (phellem)8- Laticiferous

tissue9 -Sieve tissue10- Tracheary

tissue11 -Vascular tissue12- Secretory

structures13-Nectaries

1 -ParenchymaCharacters:

1 -Simple living cells.2 -Have primary

cellulosic thin wall with simple pits.

3 -Have intercellular spaces.

4 -They may be elongated,

isodiametric or lobed.

Occurrence:

1 -In cortex and pith of stems and roots.

2 -Associated with xylem and phloem.

3 -In leaves and fruits.

Function:

1 -In aeration.

2 -In photosynthesis.

3 -Storage of water, protein, minerals, etc..

4 -May become meristematic and divide .

2 -Collenchyma

Characters:

1 -Simple living tissue.

2 -Have primary cellulosic thick wall with simple pits.

3 -May have intercellular spaces.

4 -They are elongated cells.

Types:Lamellar: thickening on

tangential walls.Angular: thickening on

angles between the cells.

Lacunar: thickening on walls facing the

intercellular spaces.

Occurrence:1 -Under epidermis of stems.2 -Cortical tissue and pericycle of

leaves.

Function: They are plastic tissue used for

mechanical support of soft plants.

3 -Sclerenchyma

They are dead cells when mature with thick secondary walls, they

are elastic tissue used for mechanical support. Sclerenchyma

has two types; fibres and sclereids.

A- Fibres

They are dead cells have pitted walled with narrow Lumina and

pointed apices, xylary fibres are lignified while extraxylary fibres may be lignified or non-lignified.

B- Sclereids

They are dead cells short, isodiametric, elongated or branched thick walled,

pitted, lignified with branched lumina.