BIOLOGY 3404FEVOLUTION OF PLANTS

Fall 2008Lecture 10

Thursday October 23Chapter 16, The Bryophytes

Part II

WHERE?

• From Arctic to Antarctic and everywhere in between, abundant in moist tropics, and a few occur in deserts.

• Like lichens, they wet rapidly but dry out much more rapidly.

• Some can survive desiccated for months or years and can survive extreme temperatures when dry, but rapid drying or extreme temperatures when wet can be damaging.

WHERE II• Epiliths (= saxicolous), epiphytes (= corticolous if on bark, epiphyllous on leaves), on soil (= terrestrial), or aquatic, but not marine

• Like lichens, are largely independent of substrate for nutrients, but may have some substrate specificity because of pH or other chemistry, or microclimate.

• Tend to be found in moist environments, bathed in surface water, because of aquatic fertilization

Bryophyte ecology and nutrition

• Bryophytes, like lichens, may take in nutrients through “leafy” tissues of thallus, in addition to uptake through rhizoids and (in a few) via symbiosis with Glomeromycota

• Because of this, they are sensitive to the environments where they live: some prefer acidic sites, others basic or calcium-rich sites; some are pollution intolerant, others tolerant

• Saxicolous, corticolous, epiphyllous, …

Economic Importance of Bryophytes

I. Liverworts and hornworts: not much! (but many contain N-fixing cyanobacteria, important in ecosystem nutrient availability; some are mycorrhizal with Glomeromycota)

II. SPHAGNIDAE: "economic" importance

• 1. Important in hydrodynamics of large areas of especially northern hemisphere - bogs and “muskeg”.

• 2. Sphagnum dressings, in medicine, shoes and diapers• III. Other mosses, various other uses

BOG FORMATION• a) open pond, slow-moving stream: margins with

floating aquatics, especially Carex spp. with roots anchored in Sphagnum

• b) Sphagnum builds above (growth) and below (death and deposition) water-line; enables margin to grow inwards

• c) increased Sphagnum growth allows colonization of mat by bog shrubs, and eventually conifers such as black spruce & tamarack

Bog Formation II• d) continued encroachment of water surface by floating

bog mat may eventually cover surface if disturbance is slight. Waves or stream-flow erode edges

• e) amelioration of water table by increased Sphagnum mat away from water-line allows development of forest; hummocks may have white pine or white birch

• f) in permafrost areas, forest lowers summer temperature of forest floor, permafrost moves upward, water is trapped, and trees are drowned, so open Sphagnum bog cycles with forest

SPHAGNUM ION-EXCHANGE MECHANISM

• Metal2+ + 2HA ---> MA+ + A- + 2H+

• Gives off H+, lowering pH and eliminating competing mosses (and many vascular plants)

• Metal ions can be displaced by shaking in H+ (e.g., dilute HCl) to assay metal content

BOG SIDE-BENEFITS

a) Bog fossils

b) PEAT (1.5m = 6,000y): for fuel and horticulture

c) Conservation aspects: exploitations and emissions

d) Carbon sink – unless climate warms!

Sphagnum dressings, in medicine, shoes and diapers

• Absorbs 16-20 X dry weight in water (cotton 4-6); comfortable; mildly antiseptic (vs diaper rash, gangrene)

• Sphagnum dressing used greatly in wars: Russo-Japanese (1904-5); WW I (both sides). Millions of dressings made by thousands of volunteers

a) crude sphagnum collected, partially air-dried, cleaned of debris, and sorted.

b) wrapped in sewn gauze

c) sterilized before use by autoclaving or with antiseptics

d) preferred species was S. papillosum; also used were S. palustre, S. imbricatum & S. magellanicum

From Prince Rupert Public Library

III. Other Mosses, Other Uses:

1. Housing2. Boat-building3. Fibre for baskets4. Bedding and pillows5. Cultivation6. Mosses as living mulch in nurseries and orchards

7. Problem mosses in lawns and roofs