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Chapter 21 Mind Map, Gametophyte and Sporophyte, Nonvascular plants,…
Chapter 21 Mind Map
Division Anthocerotophyta: Hornworts
group of small, inconspicuous thalloid plants
grow in moist soil, hidden by grasses and herbs
superficially resemble thalloid liverworts
one large, single chloroplast in each cell
the gametophyte generation
very short protonema phase
gametophores are always thin, especially along the edges
shaped like a heart, ribbon, or disc
gametophyte
brittle
does not tolerate drying
live for less than a year in temperate climates
has numerous chambers
all hornworts form symbiosis with cyanobacteria
antheridial initials are not surface cells on gametophyte
archegonia are formed from surface cells but doesn't completely surround eggs
after fertilization, zygote divides longitudinally
the sporophyte generation
hornwort foot is embedded in gametophyte tissue
no seta or discrete sporangium
meristem is located just above foot
cells from meristem push upwards and mature before dying
sporangium is a long, hornlike cylinder
at tip, sporangium is mature and open
outer layer of sterile cells is thick and chlorophyllous
spores are green, golden yellow, brown, or black
basal membrane changes activity based on moisture and temperature
Concepts
critical events in history of plant evolution
origin from green algae
adaptation to terrestrial habitats
development of vascular tissues xylem and phloem
origin of seeds, leaves, and woody growth
division of plants
neither vascular tissues or seeds (nonvascular plants)
vascular tissues but no seeds (vascular cryptogams)
both vascular tissues and sees (spermatophytes)
early plant modifications
formation of dormant, drought resistant pores
large, compact, multicellular body (water retention)
waterproof cuticle
gamete production had to be coordinated with periods of moisture
layering of cells around gamete and spore mother cells
later early plant modifications
production of phloem, xylem, and roots
production of pollen and seeds
gametophyte size became smaller and smaller
Characteristics of Nonvascular Plants
types of nonvascular plants
mosses
liverworts
hornworts
mosses
Spanish moss is not a true moss
club mosses are lycophytes
"mosses" in ponds and slow-moving streams is algae
several types of lichens are mistaken as mosses
nonvascular plants
embryophytes with no vascular tissue
has multicellular sporangia and gametangia
bodies are composed of true parenchyma cells
almost exclusively terrestrial
has a cuticle that covers most of the plant body
many have stomata
has a life cycle with an alteration in heteromorphic generations
gametophytes are the larger, more prominent generation
sporophytes
are smaller, more temporary, and often inconspicuous
never independent of the gametophyte
never branch and never have leaves
thrive in microhabitats
Classification of Nonvascular Plants
unknown how closely related the types of nonvascular plants are
three distinct divisions
liverworts, division Hepatophyta
mosses, division Bryophyta
hornworts, division Anthocerotophyta
in past, all three were classified as Brytophyta
Division Hepatophyta: Liverworts
the gametophyte generation
hepatic gametophyte have two basic groups
leafy liverworts
thallose liverworts
leafy liverwort gametophore phase
initiated when spores germinate
small, temporary protonematal phase
apical meristem is established from small amount of cells
gametophore greatly resembles that of a moss
liverwort leaves
two rounded lobes
no midrib
no conducting tissue
arranged in three clearly defined rows
leaves in two rows are much larger than third
thallose liverwort gametophore phase
flat and ribbon-like or heart-shaped and bilaterally symmetrical
thallus
body of thallose liverworts
body without roots, stems, and leaves
stratified and very thick
air pores
large chambers open to the exterior
not stomata (no guard cells)
cannot be closed
liverwort gametophores
may either be bisexual or unisexual
may be mixed with regular leaves (leafy)
may be grouped together (thallose)
small plants that have an alternation of heteromorphic generations
the sporophyte generation
little variability exists in sporophytes of liverworts
very similar to basic morphology is similar to mosses
most liverwort sporophytes have
foot
delicate seta
calyptra-covered sporangium
sporangium
globose
bright green and chlorophyllous while young
outer layer is often only one layer thick
no columella or peristome teeth
some cells do not undergo mitosis and form elaters
elaters are single, elongate cells with spring-shaped walls
elaters push spores out when sporangium opens
Division Bryophyta: Mosses
the gametophyte generation
morphology
gametophores
leafy stems
grow close together
forms dense mounds
grow from an apical meristem
leaves
aligned in three rows while young
most have a midrib
typically only one cell thick
have a thin lamellae on upper leaf surface
cuticle occurs only on the upper side of the leaf
no stomata occur on moss leaves
stems
slender with little tissue differentiation
no epidermis
little difference between outer layers and inner cells
mosses are ubiquitous, occurring in all parts of the world
water transport
hydroids
innermost cortex in some mosses
conduct water and dissolved minerals
elongated cells that lose cytoplasm when maturity is reached
each hydroid is aligned with those above and below
leptoids
species that have hydroids also have leptoids
resemble sieve cells
have relatively prominent interconnections with adjacent cells
lack nuclei at maturity but retain cytoplasm
rhizoids
located at base of stem
small, multicellular trichome-like structures
penetrate the surface of the substrate
only anchor the stem
development
protonema
network of branched cells that are similar
superficially resembles a filamentous green alga
can be distinguished by its numerous chloroplasts in each cell
eventually forms gametophore
reproduction
all mosses are oogamous
small, biflagellate sperm cells
large, nonmotile egg cells
antheridia
produces sperm
consists of
short stalk
outermost layer of sterile cells
inner mass of cells (eventually forms sperm)
archegonia
produces eggs
shaped like a vase with long neck
neck is hollow at maturity with single egg at base
the sporophyte generation
moss gametophytes
large
photosynthetic
support the sporophyte through entire life cycle
moss zygote
undergoes a transverse division
basal cell develops into small, bulbous tissue (foot)
upper cell develops into capsule
zygote foot
interface with gametophore
absorbs sugars, minerals, and water here
transfer cells in many species
zygote capsule
grows by cell division and expansion
forms a simple apical sporangium (capsule)
has an outer layer of sterile cells
has an inner column of sterile cells (columella)
zygote seta
located between foot and sporangium
is a narrow stalk
all mosses have this basic, simple structure
metabolism and ecology
two critical factors in the metabolism and ecology of mosses
small size
lack of conducting tissues
mechanisms which compensate for inability to retain water
growth in continually moist habitats
tolerant of desiccation (drying)
remarkably resistant to high or low temperatures
able to withstand intense ultraviolet light
mosses can grow on hard, impervious surfaces
mosses can grow on the surface of quiet bodies of water
Division Anthocerotophyta
Division Hepatophyta
Division Bryophyta
Nonvascular Plant Descriptions
Similarities Between Thalloid Liverworts and Hornworts
Morphology Similarities Between Mosses and Liverwort Sporophytes
