The Temple of Flora

Exploring the Biology of Plants

An obvious plant

and another

Characteristics of living things

• Growth• Nutrition• Excretion• Sensitivity• Reproduction• Movement• Respiration

Differences between plants and animals

Plants

• Have cell walls made of complex polysaccharides (eg cellulose)

• Make their own food by the process of photosynthesis, requiring carbon dioxide, water, light energy and the green pigment chlorophyll (in structures known as chloroplasts)

Kingdoms of organisms

• In simpler times:• Plants• Animals• Bacteria• Viruses• Plants and Animals are eukaryotic (ie their cells

contain a nucleus); Bacteria are prokaryotic (don’t have genetic material in a nucleus)

A historical viewpoint

• Thallophyta– Algae– Fungi

• Bryophyta• Pteridophyta• Spermatophyta– Gymnosperms– Angiosperms

More-recent changes

• Since then:Fungi no longer considered to be plantsSingle-celled organisms may be Protista‘Algae’ are several groups of unrelated

simple plants (some people don’t regard them as plants, but we’ll ignore them)

One group of algae (blue-green) now considered to be bacteria

Some modern plant groups

• Rhodophyta• Phaeophyta• Chlorophyta• Bacillariophyta• Bryophyta• Pteridophyta• Spermatophyta• (in other words, algae now seen as being several

different groups, and fungi have been removed)

Other ways of grouping plants

• Non-Flowering Plants (Cryptogams)/Flowering Plants (Phanerogams)

• ‘Algae’, Bryophytes and Pteridophytes are Non-Flowering Plants; Spermatophytes are Flowering Plants.

• Non-Vascular Plants/Vascular Plants• ‘Algae’ and Bryophytes are Non-Vascular Plants;• Pteridophytes and Spermatophytes are Vascular Plants.

Why are fungi not plants?

• Cell wall is not made of polysaccharide• Do not have chloroplasts and do not

photosynthesise

Groups of fungi

• Mushrooms and toadstools• Moulds eg Penicillium, Mucor• Rusts

Fungi

What is missing so far?

• Lichens• These are composed fungi with symbiotic algae

(rather like a fungus-alga-fungus sandwich)• The fungus provides protection; the alga

photosynthesises and produces carbohydrates which can be used by the fungus

• Classified as fungi• Interestingly, the symbiotic alga is not known in

the free-living state

Lichens

Lichen structure

Algae

• Although once regarded as a single taxonomic group, now realised that the different classes of algae are a group of plants in their own right. So, for example, Class Phaeophyceae now Division Phaeophyta

• All simple aquatic plants reproducing by means of spores of one sort or another

• Both marine and freshwater (including soil algae); multicellular and unicellular; macroscopic and microscopic

Algae

• Rhodophyta (red algae)• Phaeophyta (brown algae)• Chlorophyta (green algae)• Bacillariophyta (diatoms)• Various other groups: note, classified according to

colour (ie pigments) although their anatomy is also significantly different

• Blue-green algae (Cyanophyceae), being prokaryotic, now considered to be bacteria (Cyanobacteria) even though they have cell walls and photosynthesise

Rhodophyta: Delesseria sanguinea

Rhodophyta: Phycodrys rubens

Phaeophyta: Fucus vesiculosus

Phaeophyta: Laminaria digitata

Chlorophyta: Pediastrum

Chlorophyta: Volvox

Chlorophyta: Spirogyra

Chlorophyta: Ulva lactuca

Chlorophyta: Codium fragile

Bacillariophyta: Diatoms

Oscillatoria – an example of a Cyanobacteria

Bryophyta

• Mosses (Musci)• Liverworts (Hepaticae)

Cell Division

• Mitosis – the type of cell division which results in identical copies of the original cell – found where organisms are growing or repairing tissues. Also found in simple organisms that reproduce by ‘binary fission’

• Meiosis – cell division which results in halving the chromosome number during the production of gametes (‘sex cells’). As a result, a diploid cell (with two of every chromosome: 2n) produces haploid cells (with one of each chromosome: n). Similarly tetraploid cells (4n) produce diploid ones (2n) and so on.

More terminology

• Gametophyte – the haploid phase in a life cycle. i.e. a stage which produces haploid gametes/spores by mitosis.

• Sporophyte – the diploid phase in a life cycle i.e. a stage which produces haploid gametes/spores by meiosis.

Life cycles

• In both Bryophytes and Pteridophytes there are two stages in the life cycle.

• The moss/liverwort ‘plant’ is haploid (the gametophyte) and lives in damp conditions; the spore capsule is diploid (the sporophyte) and requires dry conditions for the spores to be dispersed.

• The fern ‘plant’ is diploid (the sporophyte) and requires more-or-less dry conditions; there is a second stage (the prothallus: haploid, tiny, and totally different in appearance) and his requires damp conditions.

Mosses

• Yet more terminology if you want it:• Acrocarpous mosses form cushions;

Pleurocarpous mosses creep across the substratum.

Mnium hornum

Mnium hornum

Tortula ruraliformis

Ptilium crista-castrensis

Hypnum cupressiforme

Sphagnum

Marchantia

Pteridophyta

• Psilopsida (Quillworts)• Lycopsida (Club-mosses: no relation to

‘mosses’)• Sphenopsida (Horsetails)• Filicopsida (Ferns)

Psilotum: Quill-wort

Psilotum: Quill-wort

Huperzia selago: Club-moss

Diphasiastrum clavatum: Club-moss

Equisetum: Horsetail

Equisetum: Horsetail

Calamites: Fossil Horsetail

Botrychium lunaria: Moonwort

Dryopteris filix-mas: Male Fern

Dicksonia: Tree Fern

Gleichenia dicarpa

Spermatophyta

• Seed plants• Gymnosperms (Conifers, cycads etc)• Angiosperms (Flowering plants):– Monocotyledons (have one seed leaf eg grasses,

orchids)– Dicotyledons (have two seed leaves – majority of

flowering plants)