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
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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
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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)
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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
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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
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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
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