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Chapter 20 - Nonvascular Plants: Mosses, Liverworts, and Hornworts…
Chapter 20 - Nonvascular Plants: Mosses, Liverworts, and Hornworts
Characteristics of Nonvascular Plants
Concepts
vascular cryptogams = have vascular tissue but no seeds
spermatophytes = have vascular tissue and seeds
nonvascular plants = bryophytes = no seeds or vascular tissues
club mosses = lycophytes
nonvascular plants = embryophytes
mosses and liverworts look like flowering plants
almost exclusively terrestrial
life cycle with an alteration of heteromorphic generations
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do not grow to be very large
We do not know how closely related mosses, liverworts, and hornworts are
Division Bryophyta: Mosses
The Gametophyte Generation
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Water Transport
hydroids conduct water
majority of mosses lack hydroids and leptoids
hydroids = water cells in innermost cortex
rhizoids = multicellular trichome-like structures
rhizoids lack chloroplasts and have reddish walls
Development
numerous small chloroplast in each protonema
protonema cells break when mosses are collected
protonema = branched system of similar cells
Morphology
all moss stems have leaves
moss stem leaves are not homologous with vascular leaves
gametophores = leafy stems
cuticle occurs on upper side of moss leaves
stems have hairs but not stomata
Reproduction
archegonia = eggs
neck is hollow at maturity
single egg located at base
shaped like a vase
bisexual species have antheridia and archegonia
antheridia = sperm
outermost layer has sterile cells
innermost cells are sperm cells
short stalk
The Sporophyte Generation
capsule = simple sporangium
seta = narrow stalk between the foot and the sporangium
foot = basal cell develops into small, bulbous tissue
operculum = separates from the rest of the sporangium
peristome teeth = complex teeth
calyptra = covering of the apex of the sporangium
Metabolism and Ecology
mosses dry out very quickly
due to thin cuticle
grow in moist habitat
mosses are small
some mosses are tolerant of desiccation
mosses are small and lack conducting tissues
mosses are important in establishment of other species
Division Hepatophyta: Liverworts
The Sporophyte Generation
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little variability
much thinner sterile layer
elaters = single, elongate cells with spring-shaped walls
The Gametophyte Generation
liverworts
small plants
have an alternation of heteromorphic generations
liverwort groups
thallose liverworts
show less resemblance to mosses
air pores
body referred to as thallus
leafy liverworts
greatly resemble mosses
rounded lobes
leaves in three rows
antheridiophore = umbrella shaped outgrowth
archegoniophores = stalked & project downward
archegoniophores and antheridiophore occur on separate plants
Division Anthocerotophyta: Hornworts
The Sporophyte Generation
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have a foot embedded in gametophore tissue
have a columella
similarities are hard to find
dies outside of plant
The Gametophyte Generation
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gametophytes have numerous chambers
zygote divides longitudinal
distinctive development
hornworts = group of small, inconspicuous thalloid plants that grow on moist soil