biology 3404f evolution of plants fall 2008 lecture 10 thursday october 23 chapter 16, the...

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