Bryophytes Flashcards
Similarities with the Chlorophyta
a) Simple thalloid body
b) Non-vascular
c) Limited tissue differentiation
d) Little/no cuticle development
e) Single, large chloroplast per cell in the simpler bryophytes
f) Reproduction depends on free water
g) Water and mineral absorption directly through thallus
h) Anchoring rhizoids analogous to holdfast of algae
i) Oogamous life cycle
j) Alternation of generations with dominant gametophyte
k) Protonema of the Hepatophyta resembles the filamentous green algae in form
General features of Bryophytes
- Simple terrestrial plants
- Inhabit moist, shady habitats
- Thalloid body
- Anchored to substratum by rhizoids
- Non-vascular plants
- Epidermal layer with poorly developed cutin-like substance
- Pigmentation
- Starch stored in chloroplasts
- These plants show a-o-g with the gametophyte (n) dominating the life cycle
Similarities with Higher Plants
- Terrestrial (amphibious)
- All macroscopic, except for the protonema
- Greater support mechanism in less dense medium of air
- Greater level of development of the gametophyte now with a differentiated epidermal layer
- Tissues produced through activity of apical meristem
- Well developed water absorbing rhizoids in more complex bryophytes
- Multicellular gametangia with protective jacket of sterile cells: Antheridia-Male and Archegonia- Female
- Multicellular sporophyte, producing many more spores in sporogenous tissue
- No zoospores (spores w/flagella) produced
- Meiospores with sporopollenin covering
- Spore dispersal by wind and water
- Many small chloroplasts per cell
Importance of bryophytes
- Provide food for herbivores, birds and other animals
- Used in bog mosses and peat mosses (water absorbing and water retaining material in seed beds and green houses)
- Used in dead and decaying mosses (humus which increases fertility of soil)
- Bioindicators of air, water pollution
- Mineral indicators
- Soil erosion control
- Chinese traditional medicine, eg. tonsillitis, bronchitis and burns
- Antimicrobial substances
- Peat reserves
- Waste water treatment
- Source of activated charcoal
- Insulation material
- Synthetic construction material, eg. peatwood, peatcreate and peatfoam
Liverworts
Phylum Hepatophyta or Marchantiophyta
Hornworts
Phylum Anthocerophyta
Mosses
Phylum Bryophyta
Phylum Hepatophyta
- The simplest group of the bryophytes
- Thallus may be:
a) Dorsiventrally flattened (eg. Marchantia sp.)
b) Leaf-like appendages on stem-like axis (eg. Bazzania sp. and Lophocolea sp.)
- Tip of each lobe has an apical notch in which the growing point is located
- Epidermis:
a) punctuated by simple raised pores that are continuous with air chambers of each areola
b) cells surrounding the pores are arranged in tiers of four
c) lacks elaborate waterproofing material
- Cells contain chloroplasts
- Lower storage/support region:
a) cells lack chloroplast
b) store starch and oils - Has unicellular rhizoids, peg rhizoids help to conduct water
Life cycle of Bryophytes
Sporic Meiosis (Haplodiplontic)
Hepatophyta- Sexual Reproduction
- Antheridia (male) and Archegonia (female) produced by mitosis on separate (n) plants (dioecious)
- The zygote develops within and is nurtured by fertilized archegonium into a multicellular embryo (matrotrophy)
- A placenta connects the new sporophyte (embryo) to the parent gametophyte through transfer cells
- As the embryo develops the venter expands, protecting the embryo by forming a calyptra (slide 34 for image)
- The sporophyte will be dependent on the gametophyte for nutrition
- When fully developed the new sporophyte is organized into: (slide 36 for image)
a) foot
b) seta
c) capsule - Meiospores then germinate to give rise to the protonema form which the thallus will develop
Antheridia (half-mushroom)
- Spherical
- Elongated
- Sterile jacket of cells
- Mass sporogenous cells
- Numerous biflagellate sperm cells
Archegonia (umbrella w/spokes)
- Flask-shaped
- Sterile jacket of covering cells
- Long neck canal
- Basal venter in which the oogonium is produced
- Bear the egg cell/oogonium
- At maturity the canal cells disintegrate and give rise to a mucus mass, in preparation for the arrival of the sperm
Foot
anchors it to the gametophyte
Seta
stalk that supports the capsule
Capsule
the sporangium (contains sporogenous cells) that produces the meiospores
Meiospores
- produced within the sporangium (sporophyte) by meiosis from sporogenous cells
- has sporopollenin walls
(slide 38 for image)
Hepatophyta-Asexual Reproduction
- Fragmentation
- Gemmae:
a) asexual spores produced in gemma cups on the adaxial surface of the thallus
Anthocerophyta and Hepatophyta Differences
(referring to Anthocerophyta)
- No dichotomus branching of the thallus
- Lobes of thallus overlap
- Guarded mucilaginous pore, connected with internal mucilaginous cavities in the thallus
- These pores are present on the sporophyte
- Monoplastidic
- Most hornwort gametophytes are monoecious
- Colonies of the mutualistic cyanobacterium Nostoc fill small cavities
- Hypodermal gametangia found sunken in pits within the thallus (no antheridiophores or archegoniophores)
- The capsule forms the major and conspicuous part of the sporophyte
- No seta
- Foot region with placenta (water minerals from female gametophyte)
- Meristematic region located at the foot of the sporophyte (‘horn’)
- Hornworts can perennate by tubers
Anthocerophyta pores’ function
assist in the drying out of the capsule and facilitate spore dispersal
Monoplastidic
only one large chloroplast in each cell of the thallus with a single central pyrenoid (has rubisco)
Monoecious
Archegonia and Antheridia are produced on the SAME thallus
Dioecious
Archegonia and Antheridia are produced on DIFFERENT thallus
Capsule of Anthocerotophyta/Hornworts
- A slender smooth upright cylindrical structure that slightly tapers the apex
- Consists of:
a) Capsule wall
b) Sporogenous tissue
c) A central (sterile) columella
d) Pseudoelaters (twist as they dry out and help to disseminate spores)
Bryophyta
- Most mosses are in this phylum
- More developed than the Anthocerophyta and Hepatophyta
- Greater resemblance to higher plants
- About 9,500 species, all of which have a “leafy” habit
- Erect axis bearing leaf-like appendages with midrib
- Multicellular rhizoids anchor the plant
Bryophyta Classes
- Bryopsida/Polytrichopsida/Bryidae (“true mosses”)
- Sphagnopsida/Sphagnidae (peat mosses)
General Characteristics of Bryophyta
- Most forms exhibit two growth habits:
a) the protonema (immature)- branching, creeping filamentous stage
b) the moss gametophyte (mature)- upright habit - Moss spores germinate to give rise to protonema, which then give rise to several gametophytes (eg. the visible moss plants)
slide 30 for image
- Many mosses have special conducting cells:
a) for water (hydroids)
b) for food (leptoids)
slide 38 for image
Protonema
a green algal-like structure
Growth habit of Polytrichum
The (heterotrophic) sporophyte generation (2n) grows out of the (fertilized) gametophyte (n).
Hydroids
- located within a central strand- hydrome
- Resemble tracheids and vessels:
a) lacking living protoplasm at maturity
b) elongate cells with slanting thin cross-walls permeable to water
c) No lignin
Leptoids
- located within a central strand of tissue called the leptom
- surrounded the hydroids within the central cylinder of the stem
- Resemble the phloem:
a) Elongated cells
b) Living protoplasm at maturity
c) Degenerate nuclei (sieve tube cell)
d) Inclined end walls with perforations
These conducting cells help to suggest the Bryophytes to be the ancestors of the tracheophytes
Bryophyta Reproduction
- The mosses are dioecious, with apical gametangia
- The male gametophyte bears the antheridial rosettes (reddish-brown colored)
- The female gametophyte bears the archegonial rosettes (green and bushy in appearance)
- Water facilitates the dispersal of mature antherozoids toward the archegonial rosettes (oogamous)
- Fertilized archegonia now develop into the new sporophytes
- These new sporophytes remain on the female gametophyte and receive nourishment (i.e. matrotrophy)
Matrotrophy
the way a baby is nourished in the mother’s womb
Spore dispersal-Bryophyta
- The calyptra (remnant of the archegonium) drops off
- The operculum is shed as a result of water loss by the annulus
- The peristome teeth bend outwards
- Spores fall out of the capsule and are carried by air currents
Peristome teeth
- triangular two-ply structures which operate like trap-doors
- differential absorption of water results in a bending of the teeth outward
- these structures are hygroscopic (tends to absorb moisture from the air)
- their movements facilitate the dispersal of the spores in conjunction with air currents
slide 47 for image
Bryophytes
- Main plant body is a haploid gametophyte
- Cuticle very poorly developed
- No true roots and leaves
- No Vascular tissue
- Archegonia with long neck having 6 rows of cells vertically
- Sporophyte is a capsule supported by a stalk (seta)
- Sporophyte is totally dependent on gametophyte
- Sporophyte is heterotrophic at maturity
