Indira Priyadarshini Govt Degree
College (Women) Nampally Hyderabad
Topic: Special Tissues or
By: T. Ramyasri
Secretory Tissues Or Simple Tissues
The cells that are concerned with the secretion Or excretion of materials
together constitute secretory tissues.
They secrete gums, resins, volatile oils, nectar latex, and other substances in
plants are called secretory tissues.
Secretion:The release of substances that have a special physiological
A] may remain in the cell producing it as
B] walled off from the cytoplasm
C] may leave the cell
excretion: separation of products eliminated from metabolism
1. External secretory structures
These tissues have special glandular structures. These glands have excretory and
secretory products. Many glandular tissues have been recognised on the basis of
position and structure present in them. Different types of glandular tissues are:
1. Glandular hairs
3. Digestive glands
secretory cells are of two types:
1.External secretory structures
2.Internal secretory structures.
1. Glandular hairs
The glandular hairs arise from the epidermis of the leaves. They
may be unicellular or multicellular,the apical portion has the
glandular structure and secretes different substances.
In Articadioca plants the glandular hairs are
unicellular. The base of the gland is wide and
becomes narrow towards the tip and the tip
is rounded. Whenever any animal comes in
contact with the top the hair penitrates in to
the skin of the animal. At the base of the sac
toxic substance is present. This toxic
substance becomes allergic to the animal by
causing irritating and itching .
In multicellular glandular hairs the apex of
the hair has cuticle lining. When the animal
comes in contact the cuticle lining breaks
and the secretory substance is released.
Eg:Labiatae, cucurbitaceae, solanaceae
The nectar secreting glands are known as nectaries entimophilous
pollinated plants secrets nectar through nectaries.
External secretory structures.
Secrete a sugary fluid called as Nectar.
Nectar attracts insects, help in pollination.
Two types of nectaries:
Floral nectaries:associated with flowers. Common type.
Extra floral nectaries:vegetative parts(petiole, pedicel,
stem) and these are common in families like verbinaceae,
Nectaries occurs in epidermis , hypodermis, trichoderm.
Nectaries have thick cuticle .
Nectar accumulate between the cellwall and cuticle.
Cuticle ruptures and release nectar.
Nectaries are associated with the vascular structures
These are seen in insectivorous plants. These plants grow in nitrogen
deficient soils. These plants kill insects and obtain nutrients from their
Eg: Pinguicula, drasera, dionea,
In Pinguicula leaves there are two
types of secretory hairs.
The hair without stalk are 2-8 celled
and secrete proteolytic enzymes
((proteases) are enzymes that break
They digest the proteins of the
The hairs present at the base and
these hairs have 16 celled apical
These cells secrete sticky substances
which helps in attraction of insects.
The glandular hairs present inside the flowers are known as
osmophores, these osmophores secrete aromatic substances.
Eg: orchidaceae plants.
Osmophores typically consist of an
epidermis of specialized secretory
cells and/or secretory
They are concentrated in certain
regions of the floral organs and can
have different shapes, sizes and
Location and structure of the
The adaxial surface at the base of each
petal displayed prominent longitudinal
ridges covered with distinct epidermal
cells that were here interpreted as
osmophores (Fig. 1).
In A. Humile, the osmophores were found
to be located on narrow ridges following
the main vascular bundles from the base
up to the longitudinal midpoint of the
Their colour was recorded as white in
anthetic flowers like the other regions of
the petals, but turning distinctly pink
later (Fig. 1A and B). In M. Indica, the
osmophores were found to be located not
only on the ridges but also covering most
of the lower half of the petals. Their
colour was yellow at anthesis, turning
brown later (Fig. 1C and D).
The water secreting structures present along the margin and the apex of the
leaves are called hydrathodes, exudation of water (guttation) takes place
Hydrathodes have a complex
It consists of a vein ending. Epithem,
a chamber and a pore.
The vein ending consists of tracheids.
Epithem is the loosely arranged
colourless parenchyma tissue. When
transpiration is less root pressure
increases, as a result exudation of
water takes place in the form of
This is seen in tomato plants
2.Internal secretory structures
These are modified secretory cells in the Parenchyma cells of cortex and
medulla. They are secretary cells, secretary cavities, laticiferous tissue.
(A) secretary cells: In plants the secretary substances are
stored in cells. These are called secretary cell or idioblaststs.
Eg: Endosperm of castor which have oilglands are called
(B) secretory cavities:The cavities with secretary substances
is known as secretory cavities. They of two types based on
their origin. They are:- 1.Lysigenous cavity & 2.Schizogenous
1.Lysigenous cavity: These are formed by the break down of
secretory cells. These cavities are lined with disintegrating
cells. The secretory cells disorganise and secretary substances
are retained within the cavity .eg:citrus ,eucalyptus oil
cavities, floral buds of cloves.
2.Schizogenous cavity: These are formed by the enlargement
of inter cellular spaces.these cavities are lined with infact
secretary cells called epithelial cells. Each of the cells has
dence cytoplasm and a prominent nucleus. Secretions are
liberated into the cavity .eg: Resin ducts, mucilage cavities,
seen in apiaceae family members and pinus leaves.
Latex Is an important plant secretion. Most commonly latex is milky white in
colour. Latex is produced in some specialised cells or group of cells known as
laticiferous tissue .
In some plants latex is yellow to orange coloured, In
some it is colourless. Laticifers are of two types:-
(a)Latex cells:These are Laticiferous cells.These are
formed from meristematic tissues. These structures are
simple initially and gradually grow along with the plant
and protrude into other tissues by dividing into branches
and branchlets.They become multinucleate due to free
Eg: These are common in plants of
(b) Latex vessels: Latex vessels are formed by the union
of several latex cells.Latex vessels may remain
unconnected Or may become connected laterally to form
a permanent work latex vessels are also called compound
laticifers or articulated Laticifers.
Eg: plants of musaceae, compositae
Rubber is extracted from latex of hevea
1. This is useful in the storage of food material.
2. These cells are useful to Mitigate the xeric conditions in desert plants.
3. Because of the presence of latex the plants are protected from animals.
4. Latex has commercial value,para rubber is obtained from latex of Havea
5. Indian rubber is obtained from the latex of Ficuselatica .
6. From the latex of sapota chiklegum is obtained. This is used in chicklet
7. Gutaparcha rubber is made from latex of palaquim .This is used in cables
.morphine is made from latex of papever somniferum.