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Plant Ecology > Lichens > Flashcards

Lichens Flashcards

1
Q

What are the photosynthetic partners to the fungi in a lichen?

A

Unicellular or filamentous green algae or less commonly cyanobacteria (which also fix N2)

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2
Q

What fungal phyla form lichens?

A

Ascomycetes (sac fungi)

Very few Basidiomycetes

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3
Q

Why are lichens given species names even if they are formed of different Kingdoms?

A

The meld of fungus and algae (or other photosynthetic partner) is so complete and each is unique that it needs to be given a species designation

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4
Q

How many lichen species have been described?

A

Over 25,000

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5
Q

What provides most of the lichen shape?

A

The fungal hyphae create the structure with cortex and medulla

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6
Q

Where is the algal component located in a lichen?

A

The inner layer below the fungal surface (upper cortex)

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7
Q

What is the reproductive structure of an ascomycete called? What is it called in a lichen?

A
  • An Ascocarp

- An Apothecium (fruiting body)

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8
Q

What is an apothecium?

A

The fruiting structure of the ascomycete fungus in a lichen

- It is a cup-shaped, spore-producing structure

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9
Q

What are Soredia?

A

Granular or powdery asexual reproductive structures of the fungus and algae

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10
Q

What are Soredia made of and where are they produced?

A

Soredia are asexual reproductive structures composed of fungal hyphae and algal cells formed on the thallus where the cortex has ruptured

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11
Q

What do soredia need once they are released?

A

They need a suitable substrate for a new lichen colony to establish

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12
Q

What are Isidia?

A
  • Small peg-shaped asexual reproductive structures
  • Produced on the upper cortex of the thallus that easily break off
  • Similar to Soredia
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13
Q

What does each partner provide in the lichen?

A

Each provides what the other cannot obtain on its own

  • Alga cell leaks carbohydrate and provides fungus with food
  • Fungus provides suitable habitat for photosynthetic partner growth
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14
Q

How does the fungus provide for the photosynthetic partner?

A

Offering suitable physical habitat by retaining water and minerals

  • facilitates gas exchange
  • Protects from intense UV
  • Deters herbivores with toxic compounds
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15
Q

What is a lichen acid? What are their properties?

A

Fungi secrete acids by secondary metabolism

  • Block UV
  • Antimicrobial capabilities
  • Bioaccumulate minerals (break down and sequester minerals)
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16
Q

What is the nature of the lichen symbiosis?

A

Mutual exploitation instead of mutual benefit

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17
Q

What environments to lichens live in?

A

Where neither the fungus or algae symbiont can live separately in abundance
- The fungi do not grow alone in the wild but algae may occur as free-living organism

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18
Q

What happens when each partner in a lichen is cultured separately?

A

Fungi do not produce lichen compounds

Algae do not leak carbohydrate food from cells

19
Q

What is haustoria and what does it do?

A

Haustoria are part of the fungus hyphae that invade and kill algal cells, but before the algae can replenish their numbers

20
Q

Why are lichens important for recently exposed surfaces?

A

Lichens are pioneers for colonizing newly exposed mineral soils and rock surfaces and start process of primary succession

  • After forest fires
  • Volcanic flows
  • Newly deglaciated surfaces
21
Q

How are lichens the pioneers of primary succession?

A
  • Lichen acids penetrate outer crystals of rocks to help break them down
  • Facilitate soil-trapping
  • Nitrogen fixing lichens add organic nitrogen (ex. lungworts)
22
Q

What are Rhizocarpon species good for?

A

Dating surfaces because they grow in concentric rings that can be counted to give a general idea of the age of a new surface that has been colonized by lichens

23
Q

What is a fact of a true epiphyte?

A

A true epiphyte cannot live on the forest floor and will die if it falls off of branch or trunk

24
Q

What happens to lichens in arid climates?

A

They don’t give up easily

They rapidly dehydrate and stop photosynthesis, grow slowly (<1mm/year)

25
Q

Why are lichens important in grasslands?

A

They stabilize surfaces and prevent erosion and ‘dust-bowl’ scenarios

26
Q

What happens to lichens in dry habitats?

A

They quickly absorb water from fog/rain and gain >10x their mass in water

27
Q

Why is reindeer lichen (Cladonia rangiferina) significant?

A
  • Provides winter food for ungulates (caribou and reindeer) in the arctic tundra
  • A reduction in this lichen due to climate change would spell disaster for the herbivores
28
Q

Why are lichens so successful?

A

They can tolerate severe temperatures and desiccation (and can provide food for some organisms in these climates)

29
Q

What can lichens bioindicate?

A

Air quality

  • Due to their ability to passively accumulate and retain contaminants, toxins, and heavy metals
  • Can therefore be used as a cheap assay material as opposed to expensive equipment
30
Q

How are lichens used as a bioindicator?

A
  • Sensitive to air pollution and decrease serves as early warning of deteriorating air quality
  • Early indicator before complete disappearance
  • Can be assayed to determine heavy metal contamination
  • Used in Index of Atmospheric Purity (IAP)
  • Re-establishment can indicate cleaner air in previously contaminated area
31
Q

IAP

A

Index of Atmospheric Purity

  • Uses lichens as bioindicator
  • Used by US forest service and air resource management programs
  • Lichens are sampled at sites and assigned numerical values for characteristics such as frequency and cover
32
Q

Foliose Lichen

A
  • Flat leaf-like growth form
  • Upper and lower cortex grow parallel to substrate
  • Loosely attach to substrate usually by Rhizines on lower cortex
  • Some may attach umbilicately
  • Can be confused with Crustose sometimes but they do have a lower cortex with rhizines unlike crustose
33
Q

What is an Umbilicate Lichen?

A

Attached to their substrate only at a central point by a cord

34
Q

Crustose Lichen

A
  • Growth form where entire lower surface is completely attached to substrate
  • Lacks lower cortex and rhizines
  • So tightly attached that they cannot be removed without damaging the substrate
  • Must take substrate when removing lichen for ID (can’t just scrape off)
  • Varied substrate types (rocks, trees, soils etc.)
  • Called Saxicolous when upper cortex isn’t visible
35
Q

What are Rhizines

A

Hyphae attachments that (loosely) attach a lichen to a surface

36
Q

Crustose Lichens on rock

A
  • Rock substrate type may indicate species (they have preferences)
  • Different mineral content may affect which lichen type will grow there
  • Most structure is inside the rock and cannot be seen (that is why substrate must be removed with lichen sample)
  • Analogous to true fungus that is mostly invisible
37
Q

Fruticose Lichen

A
  • Shrub-like growth in an upwards direction
  • Or Hanging growth in long strands often attached from a single point
  • Most 3-dimensional lichen form
  • Often round in cross-section (terete) and most are multi-branched
38
Q

Terete

A

Term for describing a round cross-section in a lichen

39
Q

Squamulose Lichen

A
  • Scale-like lichen form with lobes called squamules that are small and overlapping
  • Squamules form thallus and also occur on the podetia
  • Some may have secondary compounds and pigments such as the red on the lip-stick lichen
  • Ex. Pixie cup and Lipstick lichens
40
Q

Podetia

A

Erect structures of Squamulose lichens that can have apothecia on the top of the podetia (pixie-cup or lipstick structure)

41
Q

Chemical ID tests

A
  • Lichens can be ID’d to species with chemical spot tests
  • Spot test outer cortex or inner medulla
  • Reaction may change colour and have a positive or negative result that can be used in a key
  • Can also use a chromatogram on gel and test multiple reactions
42
Q

Packets of algae and hyphae?

A

Soredia

43
Q

What happens when a lichen is not lichenized enough?

A

It is too amorphous to be identifiable even though it may have the necessary components of a lichen

44
Q

What can outcompete or damage a lichen?

A

Mosses can kill lichens and outcompete them in moist environments
- and fungus can kill non-lichenized lichens

Plant Ecology (12 decks)

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