S1 L3 Evaluation of plant drugs

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S1 L3 Evaluation of plant drugs

• 1. Botanical
• B. Microscopy
• Cell types
• Anna Drew

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Microscopy

• Powdered plant material identified
• Via observation of the types and form of
  individual diagnostic structures present
• Presence of structures
• -gt morphological group
• Size, shape, frequency of characters
• -gt exact species
• Aided by identification tables
• Essential to recognise the diagnostic structures!

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Microscopy

• Very good analytical technique
• Quicker than extracting running a chromatogram
• Quick way to check if it is a different plant or
  material contaminated
• Magnification
• M Me x Mo
• eyepiece
  objective
• Low power x 10 x 10
  x 100
• High power x 10 x 40
  x 400

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Adjuncts on microscope

• (a) Polarized light
• Polarized material in the eyepiece
• With the analyser below it is arranged to get
  darkness
• Crystalline material may rotate planes to show
  bright
• Micromeasurement
• Micrometer eyepiece scale (100 divisions)
• Micrometer slide to calibrate the scale
• Focus micrometer slide and align with eyepiece
  scale to calibrate it for low and high powers
• Then replace with plant slide can measure
  objects in micrometres

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• 1. PARENCHYMA (ground tissue)
• Indicates plant tissue is present
• Least specialized plant cells
• Thin and somewhat flexible cell walls
• Generally have a large central vacuole
• Living at maturity
• Found in all plant organs as a continuous tissue
• cortex and pith of stems
• ground tissue of petioles
• mesophyll of leaves
• endosperm of seeds
• Also forms part of complex tissues such as
  vascular tissues
• Most metabolic functions are carried out by
  parenchyma cells
• Photosynthesis

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• Typical

Thin rounded cellulose walls
Air spaces
Isodiametric (rounded) cell
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Modifications of parenchyma

• Leaf tissue

Epidermal cell
Palisade mesophyll cell layer
Spongy mesophyll cells
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• Lignified
• Indicates secondary thickening
• Constituent of woody material

Pits in cell walls
Lignin in cell wall
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• Reticulate
• Eg Fennel fruit (Foeniculum vulgare)

Large pit (surface view)
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• 2. COLLENCHYMA
• Closely related to parenchyma
• Thicker primary cells walls (usually with uneven
  thickness)
• Living at maturity
• Role in support of herbaceous plants
• Example - the "strings" of celery
• Occur in groups just beneath the epidermis
• beneath cork in bark
• at the midrib of leaf below and above vascular
  bundle

Cellulose thickening
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• 3. SCLERENCHYMA (support cells)
• Thick secondary cell walls (showing simple
  pitting)
• Dead at functional maturity
• Cannot increase in length - occur in parts of the
  plant which have quit growing in length
• Two types
• FIBRES
• long, slender cells with a more or less regular
  secondary cell wall
• Usually occur in groups or strands
• Commercial examples flax, jute, hemp (for
  making rope)
• In dicots found in vascular tissue as xylem /
  phloem
• In monocots they may enclose the vascular bundle
  or support it either side
• Sometimes form columns from lower to upper
  epidermis
• Fibre position, aggregation and general
  appearance makes then valuable diagnostic aids
• Function support

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• Typical

Lignin
Pit (surface view)
Lumen
Pit (section view)
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Cascara bark

• Diagnostic features
• Very narrow lumen
• Found in groups
• Very thick hard to see the lumen

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Zingiber officinale (ginger) fibres viewed under
high power
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Cinchona bark fibres (viewed under low power)

• Diagnostic features
• Found singly, not in a group
• Very large
• Funnel-shaped lumen
• Striated wall
• (Some ends blunted)

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• SCLEREIDS (stone cells)
• Shorter or blunter cells with an irregular shape
• Widely distributed in plants
• Can vary considerably in shape
• Typically
• Isodiametric
• Thick secondary walls
• Numerous pits
• May occur in layers or groups or alone
• Found
• in epidermal, ground or vascular tissue
• In stems continuous sheath on the periphery of
  a vascular region
• In leaves throughout or at ends of small veins
• In fruits singly or in groups
• Hardening of seed coats during ripening often
  results from layers of sclereids
• Function
• protection (seed coats)

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• Brachysclereid stone cells

Pits in surface
Thick wall
Lumen
Eg Pyrus communis - pear
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• Astrosclereid
• TS Water lily
• Lignified
• Branched
• Single cell

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• Osteosclereid
• Cinnamon bark
• Horseshoe shape
• One wall much thinner
• Irregular sclereid

Wild cherry bark Very irregular, sometimes
branched, (jigsaw piece)
Cascara bark Irregular, solid, many in groups
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• 4. VESSELS AND TRACHEIDS
• Xylem
• Thick secondary cell walls, often deposited
  unevenly in a coil-like pattern so that they may
  stretch
• Dead at functionally maturity
• Water/ion conduction vessels and tracheids
• storage - parenchyma
• support fibres and sclereids

• Tracheid
• More primitive
• Pits allow water to pass from one to another
• Less efficient at conducting water
• More like a fibre

• Vessel
• End walls of linear parenchyma cells breakdown
  to form continuous tubes or channels
• Only found in Angiosperms

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Lignin arrangements
HERBACEOUS
WOODY PLANTS to conduct more water
Bordered pitted
Sclariform
Annular
Spiral
Reticulate
Eg Male fern rhizome
Eg Liquorice root
Eg Gentian root Rhubarb
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Gentiana lutea (Gentian) root vessels (viewed
under high power)
Tracheids of Atropa belladonna root (viewed under
high power)
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• 5. PHLOEM
• Not strong tissue collapses (as it grows)
• Not good diagnostically
• Involved in transport of sucrose, other organic
  compounds, and some ions
• Living at functional maturity
• Protoplast may lack organelles and nucleus,
  though
• End walls connect to each other via sieve-plates
• Two types of cells in the phloem
• Sieve-tube members - actual conduit for sucrose
  transport
• Companion cells - has a nucleus that may also
  control the sieve-tube element and may aid in
  sucrose loading

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Holes in patches -sieve plate at an angle
Companion cell
Sieve area - conducts to next cell
Sieve plate
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• 6. LEAF EPIDERMIS
• THE CUTICLE
• Separate outer layer made of cutin, a fatty
  substance
• Characteristic feature of epidermis
• Sometimes striated diagnostic feature

Mint
Senna
Atropa belladonna
Digitalis
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• (b) EPIDERMAL CELLS
• Continuous layer of cells covering surface of
  plant
• Elongated parts of plant, stem or petiole, cells
  elongated
• Leaves, petals, ovaries, ovules cells have wavy
  anticlinal walls and are roughly isodiametric
• In some plants they have special features
• Papillae
• Cell inclusions (tannins, crystals)
• (c) STOMATA
• Openings in epidermal cell layer
• Each stoma is bounded by two specialised guard
  cells
• These control opening and closing of the pore by
  changing their shape

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Anomocytic
Anisocytic
Paracytic
Diocytic
Senna
Mint
Digitalis
Belladonna
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• 7. TRICHOMES (Hairs)
• Protective
• Highly variable appendages
• Glandular secretory
• Non-glandular (covering) hairs, scales, papillae
  and absorbing hairs of roots
• Can occur on any part of the plant
• Persist throughout life of plant
• When lost scar (or cicatrix) is left
• Good diagnostic feature

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Unicellular
Multicellular
Senna
Hyoscyamus Warty - Digitalis
Cannabis sativa
Anise
Stellate Witch hazel
Glandular
Hyoscyamus
Digitalis Belladonna
Belladonna
Unicellular stalk
Multicellular stalk
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• 8. PERIDERM (Cork)
• Protective tissue
• Replaces epidermis in stems and roots that have
  continuous secondary growth
• Comprises
• Cork tissue (phellem)
• Cork cambium (phellogen)
• Parenchyma (phelloderm)
• Phellogen can arise in epidermis, cortex, phloem
• Produces phellem to outside
• Produces phelloderm to the inside
• Cork particularly diagnostic
• Characterised by suberisation suberin a fatty
  substance which covers (lignified) primary cell
  wall
• Cork cells vary in thickness, colour

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• 9. POLLEN
• Produced in anthers
• Varies considerably in size, shape, external
  characters
• Can be useful diagnostically for drugs containing
  floral parts