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Chapter 20 (characters of nonvascular plants (embryophytes (do not have…
Chapter 20
characters of nonvascular plants
embryophytes
do not have vascular tissue
reproductive cells surrounded by sterile cells
multicellular sporangia and gametangia
bodies made of true parenchyma
cuticle covering most of their body
heteromorphic generations
nonvascular plants life cycle
sporophyte and gametophyte
differ from each other structurally
sporophyte
tiny in nonvascular
temporary
inconspicuous
never independent of gametophyte
gametophyte
larger
more prominent generation
any familiar green moss
photosynthetic, perennial, and rapid asexual production
classification of nonvascular plants
3 distinct divisions
liverworts, division Hepatophyta
mosses, division bryophyta
hornworts, division anthocerotophyta
old theory: 2 classes
mosses, Musci
liverworts, Hepaticae
hornworts, anthocerotae
grouped in division bryophyta
just as 3 classes
division bryophyta: mosses
The Gametophyte Generation
mosses are ubiquitous
they are all over the world
in almost every environment
they are perennial
morphology
gametophores
leafy stems
grow close together
tightly appressed and forming dense mounds
cuticle
only occurs on the upper surface
underside in uncutinized
lack of cuticle
no protection from desiccation
when microhabitat dries, so do leaves
water trasport
hydroids
in primarily the polytrichaceae family
composes the innermost cortex
conducts water
dissolves minerals
leptoids
if they have hydroids they probably have leptoids
resemble sieve cells
prominent interconnection
lack nuclei at maturity
majority of mosses lack hydroids and leptoids
water is conducted on the outside of stems
use capillary action
leaves and stems form small channels
rhizoids
at base of stem
small,multicellular trichome-like
only anchor the stem
they don't absorb water
they don't dissolve minerals
lack chloroplast
development
growth of a gametophore
begins when a spore germinates
sends out a long, slender chlorophyllous cell
cell undergoes mitosis
produces a branched system of similar cells
this network is a protonema
superficially resembles a green alga
distinguished by many chloroplast in each cell
protonema
perennial
can grow extensively
can produce many buds
filamentous cells
usually break when mosses are collected
tuft of gametophytes may appear
all arisen from a single protonema
reproduction
gametophyte produce gametangia
mosses are oogamous
meaning they have small sperm cells
they also have large nonmotile egg cells
antheridia
microgametangia
where sperm is produced
consists of a short stalk
outermost layer of sterile cells
inner mass of cells that turn to sperm
archegonia
megagametangia where eggs occur
shaped like a vase with a long neck
neck is hollow at maturity
single egg is located at the base
the sporophyte generation
foot
bulbous tissue
interface with the gametophore
absorbs sugars, minerals, and water
its cells are transfer cells
capsule
simple apical sporangium
outer layer of sterile cells
inner column of sterile cells
seta
narrow stalk
between the foot and sporangium
operculum
cap like lid
separates from the rest of the sporangium
cells torn apart
peristome teeth
caused by cell breakage
exquisitely complex
respond to humidity
trapping spores when humid
division hepatophyta: Liverworts
liverworts
small plant
alternation of heteromorphic generations
the gametophyte generation
Hepatic Gemetophytes
divided into 2 groups
thallose liverworts
less resemblance to mosses
not leafy at all
instead are flat
occasionally ribbon like
bilateral symmetry
thallus
what the body is referred to
no root,stem, or leaves
thicker than those of leafy liverworts or moss
leafy liverworts
no midrib
no conducting tissue
gametophyte resembles that of moss
air pores