Tuesday, 23 November 2010

Herbal Lichenology

Todays class was an introduction and look at the world of fungi and lichens - shown on two seperate blogs.

In the morning session, Louise Olley took us through herbal lichenology: identification and uses of lichens. There is a lack of expertise in the UK - hence the use of lichen's is not really embraced in western medicine.

A lichen is formed from a fungi and an algae - it's a symbiotic relationship between the two. The fungi fruit i.e. the mushroom, is the fruiting body, while the rest is below ground.
The fungi contains the protective substances e.g. protection from desiccation, herbivores and UV light, while thhe algae provides the nutritional source from photosynthesis.
The relationship between the fungi and the algae is referred to as symbiotic, they both benefit, however the exact function of the relationship isn't exactly known. The result of this relationship, the lichen thallus, can exploit many different habitats, such as the top of everest, or even car moulding - where other botanicals struggle to grow.

"thallus" is the main body of the botanical i.e. the plant
"fruiting body" is like the flower, its the sexual reproductive part of the plant

There are four different thallus types for identification:
"fruticose" - this thallus type has two algal layer's, resulting in it being green all the time, for maximum photosynthetic orientation (to capture the most light).

"foliose" - this thallus type looks "leafy", the algae is on the upper side of the leaf, its greener as this is where photosynthesis happens, whereas the lower side contains no algae and is darker, and usually against the trunk or rock base what it is growing on. This thallus type also has small root like structures to help it attach to its growth surface, called rhizines.

"crustose" - this thallus type becomes integrated with the surface to which its growing, looking microscopically at the botanical, the root structures can be seen growing between the cracks in the rock.

"leprose" - this thallus type is often mistaken for algae, its powdery and moves quite easily when touched.

Lichen's disperse themselves easily, when touched by animals or passing movement, they break off - they're fairly brittle - also referred to as fragmentation.

"soredia" - pustulate bundles, are the lichen's reproduction system. The soredia is a fungal hyphae surrounding algal cells - they are usually seen in clusters.

There are several different fruiting bodies that can be displayed on the thallus. Examples of fruiting bodies are:
- Apothecia - nicknamed "jammed hearts" with either a lecidine (no margin) layout or a lecanorine (thaline margin, the fruits are part of the thallus, hence the same colour)
- Perithecia - small pimplese, cones, with a hole in the top
- Podetia - nicknamed "pixies cups"
- Pin heads
- Arthonioid - nicknamed "squashy messes" - no obvious structures - look like smudges on the surface
- Lirellae - nicknamed "script lichens" - look like ancient writing and have been mistaken as such

Lichen's have many uses, such as:
- Fibre (clothing, housing, cooking, sanitation)
- Fuel
- Navigation
- Insect repellent/insecticide
- Preservatives (for food or beer)
- Narcotics
- Tanning (Lobaria pulmonaria)
- Fermentation (Lobaria pulmonaria)
- Camouflage

- Food - mystery death of Caribou, moved off habitat in response to food shortage, same lichens in different area were more toxic / used for famine or eaten as a delicacy / very low nutritional value

- Perfumes and Cosmetics - 'oak moss' forms the basis of certain exclusive perfumes because of its musk-like fragrance and fixative properties - holds the smell together when the alcohol evaporates (guarded secret) / ingredients lists only state "contains lichens" but doesn't state which

- Medicine - The Doctrine of Signatures - God was giving you the answer, find a plant that looks like the body part of disease to cure it

- Embalming - light-weight, highly absorptive, delays decay, antibiotic, aromatic - helps towards mummification, stops haemorrhaging - historically used to stop bleeding

- Poison - The Wolf Lichen (Letharia vulpina) was used in Scandinavia to cul the wolf population.

- pH indicator - litmus means 'coloured moss' but its actually lichens that are used to make litmus paper - the filter paper has been treated with a natural water-soluble dye - now replaced by a synthetic version.

- Dyes - brown and red dyes are extracted from Parmelia and Evernia they're used to dye wool and produce the "Harris Tweed" of Scotland / Orchil (purple dyes) are the earliest documented dye used in Ancient Rome for the togas

- was used to form the first talcum powder - ground up mixed with rose petals - used on wigs and as a body powder - used for the smell and to kill headlice.
- was used for wadding in an old shotgun
- used as flavouring in middle eastern bread

Lichens in dermatology:
"Lichen Planus" is a skin disease, so named because it looks lichen growing on the skin, has no relation to the lichen.
Lumbermen - contact dermatitis through overexposure, leading to eczema and skin complaints - very rare today as machines are used.

Lichens are also used as hallucinogens, Amazonian tribes in Equador use tropical lichens to achieve trance-like states. Nenendape causes intense hallucinations - the Huaorani use it to call upon malevolent spirits to curse people. However these lichens used to cause sterility - it was very potent. There form of protection or of monitoring population numbers?

After Louise Olley's lecture, we had a practical session, from bags of mixed lichens we firstly had to seperate the different thallus types - of which there were three in the bag: foliose, fructicose and crustose:

Our next task was to tell the difference between Usnea and Bryoria - commonly known as "Old Mans Beard". The two lichens look identical (spare the colour difference in these photos), to tell the difference the lichen's must be wetted and then you have to pull them apart, taking a thicker stem and slowly seperating it.
Bryoria just breaks when wet, however, Usnea stems have an inner core, and when pulled apart the outer core breaks easily, but you'll find the inner core is slightly more elastic and takes slightly more before it breaks - similar to a tendon.

Bryoria is on the left, Usnea on the right, and below is Usnea's outer and inner cores.

Random interesting facts:
To put the lichens in the herbarium, they must be put in a deep freeze for four days, to kill any bacteria or contaminents, this however does not kill the lichen.
If a lichen is taken from the herbarium and water is added to the specimen, there is a possibility the algae may reform.
Lichen's can also survive for up to two weeks in an outer space vaccum, however they do lose the ability to reproduce effectively.

The second part of the day continued after the lunch break, and will be updated on a seperate blog post.

No comments:

Post a Comment