Epidermis

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Epidermis

  1. 1. 1/13/2010 EPIDERMIS Outermost layer of cells of organs in primary growth In most plants, uniseriate Multiseriate– M lti i t may originate f igi t from: a] ground meristem hypodermis b] protoderm multiseriate epidermis EPIDERMIS MULTISERIATE EPIDERMIS Results from periclinal division of protoderm Occurs late in ontogenic stages eg. Ficus elastica Moraceae, certain Begoniaceae Velamen water storage CELLS IN THE EPIDERMIS A. ORDINARY EPIDERMAL CELLS A] ordinary epidermal cells Closely attached to form compact layer B] single cell or groups of cells with special Devoid of intercellular spaces structure; form or content Conifer very thick and lignified C] cells connected with stomata ll t d ith t t Cutin is present in the outer wall D] epidermal appendages complex of lipid derivatives deposition outside the cell forms CUTICLE layer 1
  2. 2. 1/13/2010 Cuticle proper cuticularization (secretion of CUTICLE cutin to the surface of the cell wall Present in all parts of herbaceous stem, leaves Cuticular layer cutinization (deposition of Absent in actively growing parts of the roots cutin between the cellulose microfibrils of the outermost wall layers Thicker plants in dry habitats Pectin layer Two layers: 1] cuticle proper (outer; cutin) Epicuticular wax depostion of wax on the 2] cuticular layer(inner; cutin+wall surface of cuticle; granulated or rod-like or materials) continuous layer gives the “bloom” of many leaves and fruits WAX affects the cuticular permeability and the degree to which a surface can be wetted Reduces damage to photosynthesis and heat load of leaves LIGNIN Rare When present, it is found in all walls or only in outer wall Eg. Cycadaceae, needles of conifers 2
  3. 3. 1/13/2010 STRUCTURE OF PROTOPLAST OF ORDINARY B. EPIDERMAL CELLS WITH SPECIAL EPIDERMAL CELLS STRUCTURE OR CONTENT Highly vacuolated In Gramineae: Contain leucoplasts --- long cells and short cells Numerous mitochondria, ER, spherosomes, *short cells silica cells and cork cells dictyosomes di t --- bulliform cells thin walled and large vacuole chloroplasts - devoid of chloroplasts Anthocyanins –in flowers, in boat of moses lithocysts– Acanthaceae, Moraceae, Urticacaceae, Cucurbitaceae C. CELLS ASSOCIATED WITH STOMATA Minute openings or intercellular spaces limited by guard cells– stomata Stoma= opening +guard cells Stomatal apparatus or comples = stoma + St t l t l t subsidiary cells 3
  4. 4. 1/13/2010 TYPES OF STOMATA BASED ON ONTOGENY a. mesogenous -- subsidiary cells (SC) and guard cells common origin b. Perigenous b P ig -- SC develop from protodermal cells adjacent to the stomatal mother cell c. Mesoperigenous - cells surrounding the stoma are of dual origin STOMATA aerial portion of plant; esp. on leaves Absent in roots Floating water plants – upper side of leaves only l Land plants – lower surface or both Plants in full sun environment /high photosynthetic capacity--both STOMATA Arrangement > random in plants with reticulate venation > arranged in parallel row with parallel venation Position relative to other epidermal cell > level > raised > sunken 4
  5. 5. 1/13/2010 Substomatal chamber Opening of stomata Shape > kidney shaped > dumb bell shape/ elongated (Gramineae; Cyperaceae) MAIN TYPES OF STOMATA (EUDICOTS) Anomocytic (ranunculaceous) Anisocytic (cruciferous) Paracytic (rubiaceous) Diacytic (caryophyllaceous ) Actinocytic --uncommon 5
  6. 6. 1/13/2010 MAIN TYPES OF STOMATA (MONOCOT) 1] 4-6 subs. cells 2] 4-6 subs. cells; 2 round, smaller than the rest, situated at the end of guard cell 3] Guard cells are accompanied laterally by 2 G d ll i d l t ll b subs. Cells 4] guard cells are not assoc. with any subs. cells ONTOGENY OF STOMATA TYPES OF STOMATA DEVELOPMENT (BASED ON ORDER OF APPEARANCE OF STOMATA) STOMATA FREE REGIONS Basipetal – parallel venation inhibition of additional stomata by already --from the tip of the organ to its base differentiated ones No pattern– reticulation venation Formation of stomata together with the surrounding cells as part of the same developmental pattern Induction of stomata pattern by the pattern of the underlying tissue (mesophyll) 6
  7. 7. 1/13/2010 D. EPIDERMAL APPENDAGES TRICHOMES Unicelluar and multicellular-- Trichome 1. Non-glandular Massive structures such as warts, prickles a. simiple unicelluar or multicellular, uniseriate, (epidermal and subepidermal)– emergences non-flattened hairs TRICHOMES—may be lignified, with secondary TRICHOMES b lig ifi d ith d b. b squamiform h i fl t and multicellular if hairs—flat d lti ll l wall or lose their protoplast *sessile scale -- has taxonomic implications *stalked peltate *dendritic c. multicellular hairs– stellate; branched candelabrum-like d. T-shaped hairs TRICHOMES 2. Glandular d. Mucilage secreting - secretion of various substances (salt, sugar as e. Glands of carnivorous plants in nectar, lipids, gums) f. Trichomes secreting lipophilic materials -possess endodermal cells (prevents backflow) possess g. colleters- secreting sticky substances - sessile or stalked a. salt-secreting trichomes h. Stinging hairs b. Trichome-hydathode c. nectar-secreting 7
  8. 8. 1/13/2010 3. Root hairs- tubular elongations of epidermal cells - appear beyond the meristematic region - viable for a short period i bl f h t i d 8

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