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  1. Indira Priyadarshini Govt Degree College (Women) Nampally Hyderabad Subject: Botany Topic: Special Tissues or SecretoryTissues By: T. Ramyasri B.Indu
  2. 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. Secretory structure  Secretion:The release of substances that have a special physiological function. A] may remain in the cell producing it as droplets . B] walled off from the cytoplasm C] may leave the cell  excretion: separation of products eliminated from metabolism
  3. 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 2. Nectaries 3. Digestive glands 4. Osmophores 5. Hydrathodes secretory cells are of two types: 1.External secretory structures 2.Internal secretory structures.
  4. 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 . Eg:Tragia  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 plants.
  5. 2. Nectaries 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, bignoniaceae.  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 (phloem)
  6. 3.Digestive glands These are seen in insectivorous plants. These plants grow in nitrogen deficient soils. These plants kill insects and obtain nutrients from their bodies. Eg: Pinguicula, drasera, dionea, nepenthes.  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 down protein.  They digest the proteins of the insects.  The hairs present at the base and these hairs have 16 celled apical cells.  These cells secrete sticky substances which helps in attraction of insects.
  7. 4.Osmophores 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 parenchyma.  They are concentrated in certain regions of the floral organs and can have different shapes, sizes and colours .
  8. Location and structure of the osmophores  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 petals.  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).
  9. 5.Hydrathodes The water secreting structures present along the margin and the apex of the leaves are called hydrathodes, exudation of water (guttation) takes place through hydrathodes.  Hydrathodes have a complex structure.  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 droplets.  This is seen in tomato plants ,grasses.
  10. 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 secretory cells. (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 cavity. 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.
  11. Laticiferous tissue 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 (B)Latex vessels (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 nuclear divisions. Eg: These are common in plants of Euphorbiaceae,Asclepiadaceae, Apocyanaceae. (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 brasiliensis.
  12. Economic Importance 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 brasiliensis. 5. Indian rubber is obtained from the latex of Ficuselatica . 6. From the latex of sapota chiklegum is obtained. This is used in chicklet making. 7. Gutaparcha rubber is made from latex of palaquim .This is used in cables .morphine is made from latex of papever somniferum.