BIO
201: Botany
NONVASCULAR LAND PLANTS - BRYOPHYTES
This is all in chapter 20 of Stern
Life Cycle: alternation of generations with gametophyte dominant
Features:
1)
Development of enclosed sex organs
female = archegonium
male = antheridium
2)
Sporophyte develops attached to (parasitic on) the gametophyte
3) Lack
vascular tissue - must live near or in water
Three groups: (recognized at level of Division/Phylum)
Mosses – Division Bryophyta
gametophyte leafy and grows vertically
some elongate water conducting tissues present
gametophyte reproductive organs not stalked
sporophyte with columnella
Liverworts – Division Hepatophyta
commonly thallose and grows flat on substrate
gametophyte develops stalked reproductive organs
sporophyte small, lacks columnella within sporangium
Hornworts – Division Anthocerophyta
gametophyte thallose and grow flat on substrate
gametophyte reproductive organs not stalked
sporophyte with columnella
MOSSES (Division Bryophyta) – pp. 381-385
Morphology:
Leaf-like structures are not true leaves - lack
vascular tissue
Not restricted to moist habitats - but need water to
grow
distinct adult and juvenile forms to gametophyte
generation
juvenile = protonema -
look like a filamentous green algae
Asexual
Reproduction - three possible methods
1) branching of "stems"
2) formation of propagules
3) protonema: numerous juvenile plants
Sexual
reproduction - plants dioecious (fig 20.13, p. 383)
organs produced in apex of leafy stem
1) antheridia with surrounding modified thickened leaves (fig
20.12, p. 382)
individual antheridia separated by paraphyses
structures include: a) sterile jacket layer, b) stalk, c) spermatogenous tissue,
and d) paraphyses
sperm produced by mitosis
2) archegonia without thickened leaves (fig 20.11, p. 382)
structures include: a) neck canal cells, b) venter,
c) stalk, and d) paraphyses
egg produced by mitosis in venter
sperm transfer by splashing rain water
Sporophyte development (check them out on p. 384)
embryo develops a long stalk = setum
spores produced in terminal capsule
within capsule is
columnella (central internal stalk)
top of capsule -
operculum with peristome teeth that are hygroscopic
Note: hygroscopic means
sensitive to humidity
spores wind dispersed as peristome teeth allow
dispersal
spores germinate into juvenile plants = protonema
highly branched filaments
can distinguish from algae: rhizoids, developing buds
Usual
moss = Sphagnum
grows in peat bogs which produce peat moss
major component
produces an acidic pH
stems filled with many water-filled spaces which allow for water holding
during drought
LIVERWORTS (Division Hepatophyta) – pp. 377-380
Morphology - thallose forms with distinct upper & lower surface (fig 20.5, p.
378)
commonly have distinct equal branching = dichotomous
internal anatomy with photosynthetic above storage tissues
dorsal pore for gas exchange (permanently open)
ventral rhizoids for attachment
Asexual
Reproduction - two methods (fig 20.6, p. 379)
1) dichotomous branching
2) gemmae cups produce little multicellular propagules
Sexual
Reproduction - stalked structures with one sex only
(fig 20.6, p. 379)
Antheridiophores - produce antheridia on upper surface (fig 20.4, p.
377)
each antheridium contains an outer sterile jacket layer
produces many sperm by mitosis (with flagella)
Archegoniophores - produce archegonia on lower surface
(fig 20.4, p. 377)
each archegonium produces only one egg
include: neck canal cells,
venter, stalk (but NO paraphyses)
Sperm gets from antheridium to archegonium via rain splash
Sperm swims down neck canal to egg
Sporophyte development:
Zygote develops into the sporophyte on gametophyte
structures include: a) foot, b) stalk, c) capsule (fig
20.7, p. 380)
capsule includes spores
(produced by meiosis) and elators (hygroscopic and aid dispersal of
spores)