Botany LS 1203 - Plant Biology
Algae and Lichens

Algae 

Kingdom Protista

includes
    animal-like organisms:    
        euglenoids, protozoa
    fungal-like organisms:    
        myxomycota (plasmodial slime molds)
        oomycota (water molds, like potato blight)
    plant-like organisms:  
        green algae (Chlorophyta) 
        stoneworts (Charophyta)
        red algae (Rhodophyta)
        brown algae (Phaeophyceae in the Chromophyta)
        diatoms (Bacillariophyceae in the Chromophyta)
        dinoflagellates (Dinophyta)
       

photosynthetic pigments
primary for plants, algae:  chl a
Accessory pigments:    
        chlorophyll-type molecules:  chl b, chl c, phycobilins
        carotenoids:  carotenes (β-carotene), xanthophylls  (lutein, fucoxanthin, peridinin)


Green  Algae (Phylum Chlorophyta)

> 7,000 species ==> second largest group of algae

multicellular, unicellular, filamentous, colonial

mostly found in fresh water, but a fair number are marine or terrestrial (soil, tree bark)

chl a, chl b, and same carotenoids as in land plants

with fungi, can form lichens


Stoneworts (Phylum Charophyta) 

include Chara and other stoneworts; considered by some to be in the Chlorophyta (green algae) as their pigmentation and other chloroplast/photosynthesis features are the same as the green algae
have the same process to divide cell contents (cytokinesis with cell plate formation) as the land plants, plasmodesmata, apical growth, nodes and internodes 
share common ancestry with the land plants


Red  Algae (Phylum Rhodophyta)

among the oldest eukaryotic fossils known, > 2 billion years old

> 5,000  species

mostly marine, especially in warm, tropical waters

generally grow attached to something; some are free

multicellular, filamentous, or unicellular

chloroplast pigments:  chl a, phycobilins, carotenoids
    These pigments allow the red algae to live in deeper water than the other types of algae; deeper water is found beyond the tidal zone, so it is a more stable water environment

cell walls:  cellulose, agar, carrageenan

coralline algae have calcium carbonate in their walls
build coral reefs, even more than corals do.  Also serve as food for reef inhabitants (so do diatoms).


Brown  Algae   (Phaeophyceae in the Phylum Chromophyta)

mostly marine; predominantly in temperate and cold oceans

> 1,500 species known

large species have distinct structures analogous to structures of vascular plants:  holdfast (for anchorage to a substrate), stipe (a stem-like structure that sometimes has rudimentary conducting tissue), and a blade (leaf-like).  Air bladders for buoyancy are also sometimes present.  No unicellular or colonial brown algae are known.

cell walls of cellulose and alginic acid (algin, alginates)

chloroplasts have chl a, chl c, and carotenoids (esp. fucoxanthin)

shoreline:  find Laminaria
open ocean: Sargassum
kelps generally up to 70 m long


Diatoms   (Bacillariophyceae in the Phylum Chromophyta)

largest group of algae; ~20,000 described species; actual number could be ~100,000

major producer in aquatic systems

estimates put them at providing c. 25% of the total primary production on earth 

fresh and marine forms; mostly unicellular

chl a, chl c, carotenoids (esp. fucoxanthin)

cell walls contain silica  ==>  diatomaceous earth (diatomite)
The silica walls of diatoms have a lot of surface area and are highly absorptive.  This property means that scarce minerals stick to diatoms.
Also, a silica wall requires less energy to make compared to a cellulose wall (only c. 10%).


Dinoflagellates  (Phylum Dinophyta)

important producers in warm, tropical oceans

mostly unicellular

chl a, chl c, brownish xanthophylls (esp. peridinin)

outer covering of cellulosic plates

some are heterotrophic, living as parasites on fish and other protists

some are bioluminescent

cause most red tides (not necessarily red:  brown, yellow, green, etc.; not necessarily toxic); not all dinoflagellates form red tides
predominant cause of red tides off the Gulf coast and the coast of central California 
some dinoflagellates produce neurotoxins; shellfish and fish can contain the toxins. The concentration of the toxins increases as you go up the food chain; the toxicity decreases once the bloom is over.  Humans can get sick from eating contaminated fish (ciguatera) or shellfish (paralytic shellfish poisoning).
cause of the blooms:  increased mineral nutrients (runoff, upwelling of oceans); source of the dinoflagellates for the bloom:  cysts in sediments
______________

Algal blooms in general
increased P in water (from runoff) increases algal growth
the algae die; decomposition uses up O2 in water; fish die


The Economic Botany of Algae

Food Algae

Japan:
    Kombu (Laminaria, a brown alga)  
    Nori (Porphyra, a red alga)    Nori has been cultivated in Japan for >300 years on submerged rope beds.
    Wakambe (Undaria, a brown alga)

Limu (Hawaii):  uses many genera, including Ulva (a green alga, also known as sea lettuce)

Ireland:  Irish moss (Chondrus crispus, a red alga):  carrageenan, blanc mange

Cell Wall Products:

alginic acid (from Laminaria, Macrocystis):  ice cream and other dairy products, shaving cream, paint, to thicken dye pastes in the textile industry, for making dental impressions

carrageenan:  stabilizing and thickening agent for  paints, cosmetics, dairy products (like sour cream, ice cream, egg nog, and chocolate milk), instant pudding,  toothpaste, creamed soups

agar:  to gel growth media for microorganisms (bacteria, fungi) and plant tissue culture
    used in mayonnaise, pudding, lotions

Algae harvested for wall products:
Chondrus crispus (Irish moss) = harvested in Ireland as a source of carrageenan
Eucheumu = grown in the Philippines for carrageenan
Gracililaria = agar
Macrocystis, a kelp harvested off the Pacific coast of North America for alginic acid.  It is cut several times a year, ~ 3 m below the water surface.
Diatoms:  diatomaceous earth is used as a filtering agent, for insulation, as a mild abrasive.  1 cm3 = 4.6 million diatom shells.  Essentially insoluble and extremely heat resistant.


Algae  of  Local  Interest

Dunaliella

D. salina = grows in GSL; harvested as a source of β-carotene
To live in a saline environment than can be up to 10x saltier than sea water, D. salina  stores carbohydrates as glycerol (not starch) which will help the alga maintain its water balance.  The glycerol can make up as much as 30% of a cell’s dry weight.  Under stress conditions, the alga makes large amounts of β-carotene; the  β-carotene can account for up to 20% of a cell's dry weight.

Other species of Dunaliella grow in extreme environments other than saline lakes, like acid hot springs.
Dunaliella acidophila
Cyanidium caldarium
Galdieria sulphuraria - can grown in the rocks  around the hot spring
Within the rocks,  the upper layers of the alga near the rock’s surface are the  primary producers, and the algal layers further into the rock are consumers dependent on the surface cells.  


Pink  Snow  (Watermelon  Snow)


Noticeable in the summer in lingering snow banks at high elevation (like Snowbird)
Due to unicellular green algae
About 60 species have been observed in the western US.  The red color comes from carotenoid pigments.
The algae might live up to 25 cm (10 inches) deep in the snow.
1 tsp of melted snow can have > 1 million algal cells

The algae in pink snow are the producers for a very small ecosystem:
bacteria and fungi breakdown windblown detritus, pollen, dead algae and insects
algae do photosynthesis
algae feed protozoa, nematodes, snow worms, rotifers
these organisms feed mites, spiders, and insects
these organisms feed birds


Algae and Animals:  flamingos, polar bears, and sloths


Lichens

Ascomycete (rarely, basidiomycete) + green alga or cyanobacterium or both

For a long time, were thought to be bryophytes (esp. liverworts)
    1868:  Simon Schwendener described the dual nature of lichens
    1896:  Beatrix Potter proposed that the fungus and alga lived in a mutualistic symbiosis
        alga provide photosynthetic capacity (if cyanobacterium, also N-fixation)
        fungus provide protection from dessication and damaging solar irradiation; also provide better absorption and retention of water and minerals

Three growth forms:
foliose:  leaf- like appearance; loosely attached to substrate; often mistaken for liverworts.
crustose:  very thin, grow flattened against the substrate.
fruticose:  upright or hanging branches; attached at a single point (holdfast).

The fungal partner in the lichen is unique and used to ID and name the lichen.  The algal partners can be found in several different lichens.  The fungus is rarely found alone in nature; the alga can often be found living independently of the fungus.

Some think that the fungal/algal relationship is parasitic by the fungus:  the fungus forms haustoria that can be seen penetrating the algal cells; some algal cells are destroyed in the process.

Most view the relationship as mutualistic:
In nature:  the lichen can grow in habitats where neither the fungus not the alga can grow alone
In lab:  alga and fungus cultured separately will form a lichen if placed together in a medium in which neither can grow alone.

Lichens grow everywhere, from arctic and alpine tundra regions to desert, on a variety of substrates:  concrete, tombstones, rocks, roof shingles, tree trunks and branches.  A wide variety of colors is seen:  shades of green,  shades of gray, orange, red, yellow, black.

Importance of lichens:
pioneer organisms in xerosere plant successions
    can grow on bare rock and initiate soil formation
very sensitive to air pollution (sulfur dioxide) ==>  indicator species
reindeer moss, other fruticose lichens == fodder for reindeer, caribou, deer, and cattle
source of dyes == Harris tweed, litmus paper


Review

Kingdom Protista ==> home of the algae
Be familiar with the six groups of algae covered in class.
Be able to distinguish the six groups on the basis of:  accessory pigments (particularly chlorophylls/phycobilins) for photosynthesis, cell wall molecules, habitats, and diversity of growth forms and numbers of species  that are found.

What organisms are responsible for most red tides?  What environmental conditions promote the development of the red tides?  Why is fishing usually prohibited during red tides?  

Be familiar with the algal foods of island countries and states.  Which red alga has been cultivated in Japan for over 300 years?  What are the sources of other algae that are used for food or preparation of wall materials?
Be familiar with algal wall materials and their uses in the US.  Know the algae used as sources for these materials.

How can Dunaliella salina live in the Great Salt Lake?  What type of alga is D. salina?  Why does it turn deep orange/red?   Why is D. salina harvested from the GSL?
Which algae are responsible for pink snow?  
What is the importance of D. salina and the snow algae to their ecosystems?

What is a lichen?  
Know the three growth forms of lichens (foliose, crustose, fruticose)
Who first described the dual nature of lichens?  Who first proposed that the organismal relationship in a lichen is a mutualistic symbiosis?   What are the benefits to the organisms involved?
What evidence supports the view that the symbiotic relationship in a lichen is mutualistic?
What evidence supports the view that the symbiotic relationship in a lichen is parasitic?


Links

Watermelon Snow  (Wayne Armstrong:  Wayne's Word Noteworthy Plant For August 1998)

Lutzoni, F. and Miadlikowska, J. 2009. Lichens. Quick Guide. Current Biology 19:R502-R503.


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22 March 2011.  Links checked 22 March 2011.