Botany LS1203 - Plant Biology

The Plant Kingdom

The bryophytes and vascular plants will have the following features:
        chl a, chl b, carotenoids
        store starch in plastids
        cellulose cell walls 
        cytokinesis: cell plate
        sporic life cycle

Bryophytes  (Nonvascular Plants)

Three Phyla
Mosses  (Bryophyta)
Liverworts (Hepatophyta)
Hornworts (Anthocerophyta)

Features of Bryophytes

1.  lack lignin; lack xylem and phloem; lack support cells  ==>  limits size
(some mosses:  hydroids and leptoids)

2.  roots and leaves are defined by vascular tissue arrangements; therefore, bryophytes lack true roots and leaves

3.  rhizoids - for anchorage; very little absorption  (most absorption is through “leaves”)

4.  thin or no cuticle

5.  sperm require free water in order to swim to egg

6.  despite dependence on free water and limited means to conserve water, are found in a wide variety of habitats, including deserts


Mosses
~15,000 species
can reproduce asexually by fragmentation

hydroids:  resemble tracheids, the water and mineral conducting cell of the xylem.  Dead and empty at maturity.
leptoids:  resemble sieve tubes, the sugar conducting cells of the phloem

Parts of a mature moss sporophyte:
foot:  grows into gametophyte; absorbs water, minerals, and sugars from the gametophyte
seta:  the stalk
capsule:  the sporangium.  Forcibly expels the spores as it dries.  Dispersal takes several days.


Liverworts
~8,000 species 
can reproduce asexually by fragmentation, gemmae 

spore dispersal:  elaters in with spores.  Elaters dry out, twist as they dry, and disperse the spores in a few minutes.

Hornworts
~100 species 
can reproduce asexually by fragmentation
the green sporophyte that forms can live several months before releasing spores (mixed with elaters)
spores made and released over time
Nostoc (a cyanobacterium) lives in the mucilage that fills the pores and spaces of hornworts


Ecology
peat bogs —>  acid soils —>  cranberries, carnivorous plants

no roots ==>  can live on rough, hard surfaces, like sidewalks, roofs, rocks, tombstones

can survive dehydration and freezing.  Most abundant plant type in arctic places.
dehydration –>   poikilohydric, like star moss (Tortula raralis)

with lichens, are pioneers in xerosere plant successions
increase soil humus

Economic Botany of Bryophytes 
Sphagnum
moss
        - wet packing for flowers  (holds 20-25x its weight in water)
        - dry as bandages (> 1 million per month in WW I by the British)
peat:  accumulations of Sphagnum because of slow decomposition due to the acidity of the bog.  (also why "bog people" can be found); used as a soil amendment, fuel.   
See Peat Facts at the Iowa Department of Natural Resources - Geological Survey.


Review
What features of the bryophytes are common to all of the land plants and the Charophyta?
What is poikilohydry?  How is this characteristic important to plants that inhabit xeric environments? 
How do elaters aid in spore dispersal? 
Be able to distinguish between the three phyla of bryophytes. 
What are leptoids and hydroids? 


Biological Diversity:  Nonvascular Plants and Nonseed Vascular Plants  (from the Online Biology Book by M.J. Farabee at Estrella Mountain Community College) 


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22 March 2011.  Links checked 22 March 2011.