1. S1 L3 Evaluation of plant drugs
1. Botanical
B. Microscopy
Cell types
Anna Drew

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

3. Microscopy Very good analytical technique Magnification
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 x = x 100
High power x x = x 400

4. 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

10. 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
Storage
Secondary growth
Wound healing
Most parenchyma cells have the ability to differentiate into other cell types under special conditions
During repair and replacement of organs after injury
Can resume meristematic activity to produce adventitious roots and shoots

11. Typical Thin rounded cellulose walls Air spaces
Isodiametric (rounded) cell

12. Modifications of parenchyma
Leaf tissue
Epidermal cell
Palisade mesophyll cell layer
Spongy mesophyll cells

13. Lignified Indicates secondary thickening Constituent of woody material
Pits in cell walls
Lignin in cell wall

14. Reticulate Eg Fennel fruit (Foeniculum vulgare)
Large pit (surface view)

15. 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

16. 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

17. Typical
Lignin
Pit (surface view)
Lumen
Pit (section view)

18. Cascara bark
Diagnostic features:
Very narrow lumen
Found in groups
Very thick – hard to see the lumen

19. Zingiber officinale (ginger) fibres viewed under high power

20. 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)

21. 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)

22. Brachysclereid ‘stone cells’
Pits in surface
Thick wall
Lumen
Eg Pyrus communis - pear

23. Astrosclereid
TS Water lily
Lignified
Branched
Single cell

24. Osteosclereid Irregular sclereid 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

25. 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

26. 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

27. Gentiana lutea (Gentian) root vessels (viewed under high power)
Tracheids of Atropa belladonna root (viewed under high power)

28. 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

29. Holes in patches -sieve plate at an angle
Companion cell
Sieve area - conducts to next cell
Sieve plate

30. 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

31. (b) EPIDERMAL CELLS (c) STOMATA
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

32. Anomocytic
Anisocytic
Paracytic
Diocytic
Senna
Mint
Digitalis
Belladonna

33. 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

34. Unicellular
Multicellular
Senna
Hyoscyamus
Warty - Digitalis
Cannabis sativa
Anise
Stellate
Witch hazel
Glandular
Hyoscyamus
Digitalis
Belladonna
Belladonna
Unicellular stalk
Multicellular stalk

35. 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

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