Secretory Ducts And Latificers


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Secretory Ducts And Latificers

  1. 1. 1/13/2010 Secretion –the release of substances that have a special physiologic function (enzymes, (enzymes hormones) Excretion- separation of products eliminated from metabolism Secretion : A] may remain in the cell producing it as droplets B] walled off from the cytoplasm C] may leave the cell External secretory structures A. Trichome and glands B. Nectaries p C. Osmophores D. Hydathodes Internal secretory structures A.Secretory cell B. Secretory spaces C. Laticifers 1
  2. 2. 1/13/2010 Glands may release Trichomes may release - Nectar Terpenes (essential oils) - mucilages Sugars (floral and extrafloral nectaries) -digestive enzymes (insectivorous plants) digestive Water (trichomatous hydathodes) Salts (plants in saline habitats) Structure of secretory cells May occur on flowers (floral nectaries) or • Have dense protoplast, large nucleus vegetative parts (extrafloral nectaries) Mechanisms for release epidermal layer or may include subsurface layers, 1.may release secretion in between wall and cuticle * Eventually cuticle bursts (may regenerate cuticle or have dense cytoplasm may be papillate are cytoplasm, papillate, dry up after excetion) closely packed and have thin walls * Or not at all but individual cells are severed Sugars of nectaries derived from phloem Nectar excreted through 2.special mechanism (tip breaks off and contents e.g. A. cell wall and ruptured cuticle histamine escape into wound B. through stomates (that are not able to close and open) scent of the flowers produced by essential oils Originate from epidermis of perianth or from osmophores (special glands) Aristolochiaceae, Aristolochiaceae Araceae etc etc. form of flaps, brushes or cilia Emission of volatile secretion is of short duration and is associated with utilization of large amounts of storage products 2
  3. 3. 1/13/2010 A structure that discharge water from the interior of the leaf to the surface Eliminates water through the terminal tracheid in contact with epithem EPITHEM thin walled parenchyma deficient in chloroplasts and provided with intercellular spaces through which water moves through the incompletely differentiated stomata A. Secretory cells (crystal containing cells may die after deposition of the crystal or may be separated from living part of the protoplast) B. Secretory spaces In the form of spaces or cavities formed by schizogeny, lysigeny or their combination Epithelial cells of resin canals (excretion found in protoplast next to wall facing the space) Lysigenous space (oil cavities –Citrus) (excretion occurs first in intact cells before the latter breakdown) 3
  4. 4. 1/13/2010 Derived from the word latex meaning According to origin: juice in latin 1. Simple laticifer – derived from a single cell Because of the milky appearance of the 2. 2 Compound laticifer – derived from latex, it is sometimes called lactiferous union of cells cells or vessels from the latin word for milk, lac According to structure: Articulated nonanastomosing- 1. Articulated laticifer / laticiferous vessel-- compound tubes not connected with compound in origin consists chains of cells; each other laterally (Ipomoea, end walls may remain, become perforated convolvulus, convolvulus Achras sapota Allium musa) sapota, Allium, or are completely removed Articulated anastomosing – 2. Nonarticulated laticifer- (laticiferous cell) cell chains connected with each other simple in origin which through continued laterally (Hevea, Lactuca, Carica papaya, growth develops into a tube-like structure Manihot) Nonarticulated unbranched – develop more or less straight tubes (Vinca, Urtica, Cannabis) Nonarticulated branched – each cell forms branch repeatedly forming an immense system of tubes (Nerium, Ficus, Euphorbia 4
  5. 5. 1/13/2010 Liquid matrix with minute organic suspension contain: carbohydrates, organic acids, salts, alkaloids, sterols, fats, tannins, and mucilages The dispersed particles: terpenes which include essential oils, balsams, resins, camphors, carotenoids and rubber Latex may be clear or milky Flow of latex in when cut open is a pressure flow 5
  6. 6. 1/13/2010 With living protoplast retaining nucleus at functional maturity Structure of the wall Cytoplasm along the periphery surrounding the vacuolar Walls of laticifers are nonlignified and sap plastic nonarticulated - coenocytic condition; if similarly observed Arrangement in the plant in articulated forms, it is due to fusion of protoplasts generally through the plant The latex particles are formed in the cytoplasm most commonly the phloem no clear demarcation bet. the cytoplasm and vacuole may occur also in the xylem the tonoplast breakdown the escape of the latex particles into the vacuolar sap which become part of the latex (Caricaceae), cortex (Musa), pericycle, mesophyll Vital sap vessels Take part in the translocation of assimilates- association with the vascular bundles storage of food materials but not readily mobilized during unfavorable conditions form an excretory system Protection--seals wounds, as defense against herbivores and microorganisms 6