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

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!

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 10 x 10 = x 100 High power x 10 x 40 = x 400

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

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

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

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

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

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

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

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

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

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

Zingiber officinale (ginger) fibres viewed under high power

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)

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)

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

Astrosclereid TS Water lily Lignified Branched Single cell

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

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

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

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

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

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

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

(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

Anomocytic Anisocytic Paracytic Diocytic Senna Mint Digitalis Belladonna

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

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

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

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