Nonvascular Plants: Mosses, Liverworts, and Hornworts
Characteristics of Nonvascular Plants
Division Bryophyta: Mosses
Division Hepatophyta: Liverworts
Division Anthocerotophyta: Hornworts
Classification of Nonvascular Plants
spermatophytes
do not have vascular tissue
multicellular sporangia
true parenchyma
leafy stems
terrestrial
covered in cuticle, some have stomata
alternation of generations
sporophyte and gametophyte differ
green moss plant is gametophyte
look closely for sporophytes
small and simple
not known how closely these are related
many common and different features
all informally referred to as "bryophytes"
The Gametophyte Generation
mosses are ubiquitous
morphology
leafy stems- gametophores
Water Transport
dense mounds
some grow in ribbons
gametophores grow from apical meristem
Leaves are aligned in three rows
cuticle on upper surface
little protection against desiccation
hydroids
conduct water dissolve materials
leptoids
resemble sieve cells
lack nuclei
slow transport in most
rhizoid
anchor stem
Development
growth begins when spore germinates
long, slender chlorophylous cell
mitosis into protonema
organize into apical cell
grow extensively, producing many buds
Reproduction
oogamous
small biflagellate sperm cells
nonmotile eggs
sperm produced in antheridia
megagametangia- archegonia
antheridia and archegonia can occur in same or separate gametophores
antheridia bursts open when sperm cells mature
The Sporophyte Generation
zygote retained by gametophyte
megagametophytes are small
6 cells other than egg
foot
capsule
seta
sporophyte structurally complex
operculum
peristome teeth
calyptra
homosporous
Metabolism and Ecology
Small size, lack conducting tissues
cannot handle dry air
permanently moist microhabitats
some tolerant to desiccation
high or low temperatures
can grow in relative any place
small plants with heteromorphic generations
The Gametophyte Generation
leafy liverworts or thallose liverworts
initiate when spores germinate
leafy gametophytes resemble mosses
aligned in rows
oil bodies stem cells
thallose ribbon like
thallus
unicellular rhizoids
large air pores
bisexual or unisexual
antheridiophore
archegoniophores
sperm carried by rain
The Sporophyte Generation
little variability exists
foot, seta, calyptra
globose sporangium
elaters
inconspicuous
superficially resemble thalloid liverworts
The Gametophyte Generation
3-4 protonema cells
upper level smooth
mucilage
The Sporophyte Generation
foot embedded in gametophore tissue
long sporangium
thick sterile cell layers