PLANT TISSUE

Presented by:S. Konmei MukholeeM.Sc. 1st semester Department of Life ScienceBangalore University

Under the Guidance of:Dr . Prabhu B.M.

PLANT TISSUES

Plants perform functions which are different from animals and also their structure is different , hence they have tissues which are different from animals. They are further classified into many sub categories which is shown in the table below:

MERISTEMATIC TISSUE

Meristematic tissue are the growth tissue and found in those region of plant that grow continuously.

Cells of meristems divide continuously and help in increasing the length girth of the plant body.

According to their position in plant, meristems are apical, lateral and intercalary.

Functions: The main function of meristems is to continuously form a number of new cells.

CHARACTERISTICS OF MERISTEMATIC TISSUE• The cells of meristematic tissue are

similar in structure and have thin cellulose cell walls.

• The cells may be round , oval, polygonal or rectangular in shape.

• They are compact, having no intercellular space.

• There is a large nucleus and abundant cytoplasm.

• The protoplasm contains very few or no vacuoles at all.

Meristematic tissue as seen in cross section

TYPES OF MERISTEMATIC TISSUE

1. Apical meristems2. Intercalary meristems3. Lateral meristems

APICAL MERISTEM• These are situated at the

growing tip of the dicot stems and roots i.e. at shoot apex and root apex. Apical meristems are also found in the apices of the leaves.

• In plants belonging to the MONOCOT class, apical meristems are located ONLY in the root tips.

• As cells in apical meristems divide and elongate, shoot tips and root tips grow longer. This increase in length is called primary growth.

Root cap

Apical Meristem in a Root Tip

• These are located at the base of the nodes, internodes, leaves etc.

• They are also present in between the permanent tissue.

• It produce an increase of length of organ.

• E.g...stems of grasses or other monocots.

INTERCALARY MERISTEMS

INTERCALARY MERISTEMS

Monocots, like grasses, have intercalary meristems which allow the leaves to grow back after mowing.

phloem

Vascular cambium

Xylem(wood)

Cork(bark)

Cork cambium

LATERAL MERISTEMS

Cross section of dicot woody stem

PERMANENT TISSUE

• These tissues arise from the meristematic tissue.• They are non-meristematics /consisting of only one

kind of cells.• These tissues may be living or dead.

Permanent tissue is classified into two types:1. Simple permanent tissue.2. Complex permanent tissue.

SIMPLE PERMANENT TISSUE

These tissue are composed of cells which are structurally and functionally similar. Thus, this are made of one types of cells.Three categories of simple permanent tissue:1. Pollenchyma2. Collenchyma3. sclerenchyma.

The cells are living. The cells are thin walled. There may or may not be

intercellular spaces. They are the most

unspecialized cells. No depositions are seen, the

cell wall consists only of cellulose.

There is a prominent nucleus, cytoplasm & vacuoles

PARENCHYMA

ParenchymaIntercellular spaces

Storage parenchyma : The cells enlarge to store nutrients & water.Aerenchyma : Air cavities are present in the parenchyma tissue to provide buoyancy to the aquatic plants.Chlorenchyma : These parenchyma cells have presence of chlorophyll & hence can perform the function of photosynthesis.Parenchyma tissue is found generally in all parts of the plant body. It forms the Ground tissue in leaves, stem, roots & fruits etc. .

AERENCHYMA

CHLORENCHYMA

There are some special types of parenchyma tissues :

1. Parenchyma serves as packing tissue.2. By providing turgidity , they provide mechanical

strength.3. Parenchyma serves as a food storage tissue.4. Transport of material occur through cell or cell

walls of parenchyma cells.5. Parenchyma cells are metabolically active.

FUNCTION OF PARENCHYMA

COLLENCHYMA

They are located below the epidermis of dicotyledons stem and petiole.

These cells also occur in the mid rib of the dicot leaves

The cells are living. Less Intercellular space

present.They contain few chloroplast.

1. Collenchyma is a mechanical tissue and protective in function.

2. Cells are living i.e. non lignified.3. They contain few chloroplasts.

FUNCTIONS OF COLLENCHYMA

SCLERENCHYMA

Dead cells with no protoplasm. The walls of cells greatly thickened

& lignified. Due to excessive thickening of the

wall of sclerenchyma cells, its cell cavity or lumen becomes nearly absent.

The cells of are closely packed. No intercellular spaces.

No intercellular space

They are found in Stems, roots, veins of leaves, hard covering of seeds & nuts.

Sclerenchyma

There are two types of sclerenchyma cells

Fibres• Fibres are long, thickened cells with

thick lignified walls and narrow lumens. • Their walls have simple pits.• Elongated sclerenchyma cells usually

with pointed end.• fibres are found in xylem and phloem

and form bundles caps in dicotyledons stems.

They provide mechanical strength and protection to the non growing regions.

Sclereids:• Sclereids shorter and fatter than

fibres & have heavily lignified cell walls.

• They are commonly found in the cortex and pith of gymnosperms and dicotyledons.

Sclereids may occur in isolation in the cortex, pith, xylem and phloem or may occur in groups in the testa of seeds eg. shell of walnut.

FIBRES SCLEREIDSparenchyma

The complex tissues consist of more than one type of cells. All these co-ordinate to perform a common function.Complex tissues transport water,mineral salts(nutrients) & food material to various parts of plant body.Complex tissues are of following two types :I.Xylem or woodII.Phloem or bastXylem & phloem are both conducting tissues & also known as vascular tissues; together both of them constitute vascular bundles.

COMPLEX PERMANENT TISSUE

They are found in the vascular bundles of roots, stems and leaves

xylem is a vascular & mechanical tissue. Xylem is composed of cells of four

different types; vessels, tracheids xylem(parenchyma cells) and fibres.

Vessels and tracheids are very long tube-like structures formed by a row of cells placed end to end.

Functions-i. The main function of xylem is to carry water & minerals salts upward from the root to different parts of shoots.ii. Since walls of tracheids, vessels & sclerenchyma of xylem are lignified, they give mechanical strength to the plant body.

XYLEM

PHLOEM

Like xylem, it contains tubes but has no mechanical function.

phloem is composed of following four elements or cells.1.sievetubes elements; 2.companion cells;3.phloem parenchyma& 4.phloem fibres.

Except for phloem fibres, phloem cells are living cells.

Functions:phloem transport photosynthetically prepared food materials from the leaves to the storage organs & later from storage organs to the growing regions of the plant body.

Companion cell

nucleus

Sieve plate

sieve plate

PHLOEM

Sieve tube element

plasmodesmata

• It is usually present in the outermost layer of the plant body such as leaves, flowers, stem & roots.

• Epidermis is one cell thick & is covered with cuticle.

• Cells of epidermis are elongated & flattened & do not contain any intercellular space between them

EPIDERMIS

FunctionsThe main function of epidermis is to protect the plant from desiccation & infection. In fact, cuticle of epidermis helps to reduce water loss by evaporation from the plant surface as well as helping in preventing the entry of pathogens. epidermis

REFERENCES

An Introduction to Plant Biology, Mauseth, James D. 2003. Botany: 3rd Edition. Jones and Bartlett, Sudbury, MA.

“A TEXTBOOK OF BOTANY” Author Bhattacharya, Hait, Gosh volume II published 2007

“ PLANT ANATOMY” Author B.P. PANDEY, S . CHAND. “PLANT ANATOMY” Author KATHERINE ESAU . PUBLISHED by John wiley

and sons 1953.