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Ch 20. Nonvascular plants (Characteristics of Nonvascular Plants (Do not…
Ch 20. Nonvascular plants
Have neither vascular tissue or seeds
AKA bryophytes
First plants to arise
began evolving early to avoid drought
water proofing cuticle
simultaneous with evolution of stomata/gaurd cells
Multicellular body
Also escaped predators in the water
Likely gave rise to ancestors of vascular plants
E.G mosses, liverworts
Characteristics of Nonvascular Plants
Do not have vascular tissue
Xylem
Phloem
Reproductive cells surrounded by layers of sterile cells
Bodies composed of parenchyma
growth from apical meristem
Almost exclusively terrestrial
cuticle covering most of their bodies
Many with stomata
Life cycle stages
Gametophyte
The larger stage, or the "plant stage
haploid
photosynthetic
absorb minerals
Sporophyte
very small
only absorb minerals
from gametophyte
limited photosynthesis
not enough to support their own growth
Only present certain times of the year
very small size
allows thriving in microhabitats
E.g on rocks or trees
other plants cannot survive here
Classification of nonvascular plants
Three divisions
Division Bryophyta:Mosses
occur in all parts of the world and almost every environment
metabolism and ecology
low water retention
growth in permanately moist habitats
may be microhabitats
desiccation-tolerant
dormancy
can lose large amounts of water,
photosynthesis+respiration stop
different habitats
on rocks
can dissolve rock giving rise to new plants
in low temperatures
perennial
Morphology
Gametophores grow close together
form dense mounds
contain leaves
are not homologous of vascular plants
aligned in three rows
Contain a midrib
multiple cells thick
One cell thick
Except at midrib and along margin
Cuticle
Only on top surface
little protection against desiccation
No stomata
grow from apical meristem
apical meristem contains a prominent apical cell
Stems and leaves grow in precise arrangements
Stems
Slender
Little tissue differentiation
All tissues are called cortex
Walls
Somewhat thickened
Water transport
Hyroids
Conduct water and dissolved minerals
Elongated cells
Lose cytoplasm when mature
End walls
Partially digested
Leptoids
resemble sieve cells
elongated
Interconnections with adjacent cells
Lack nuclei at maturity
Only occur in some mosses
Majority of mosses lack hydroids and leptoids
water is conducted along the exterior of their stems by capillary action
Development
Gametophore growth
Begins when a spore germinates
Send out a long chlorophyllous cell
will undergo mitosis
Produces a protonema
a branched network of similar cells
will eventually develop nodules of cytoplasmic cells
1 more item...
Reproduction
Sperm
produced in antheridia
may be washed to new gametophore by rain
may swim to new gametophore
break out of antheridium at maturity
Eggs
occur in archegonia
bisexual plants have eggs+sperm on same gametophore
some species have male or female gametophores
Gametophore Generation
Sporophyte Generation
supported by gametophyte
never independent or free living
foot
the interface with the gametophore
gametophore provides nutrients
developed from the basal cell
upper cells grow into the capsule
inner+outer layer of sterile cells
meiotic sporogenous cells in-between
produce haploid spores
sporophyte
morphologically simple
structurally complex
true epidermis
with stomata
operculum
caplike lid
differentiates from the apex of the sporangium
will tear apart from the sporangium
results in two rows of peristome teeth
1 more item...
homosporous
all spores look alike
Division Hepatophyta: Liverworts
gametophore phase
two groups
thallose liverworts
flat and ribbon like
body referred to as a thallus
without roots, set,s, and leaves
air pores
similar to stomata
can't be closed, no guard cells
leafy liverworts
thin leaves
two rounded lobes
no midrib
no conducting tissue
slender stem
grows from an apical cell
tissue is simple parenchyma
apical meristem formed after a few cells have formed
sporophyte generation
little variability exists
basic morphology is basically the same as mosses
have a foot, seta, calyptra covered sporangium
has no stomata
some cells undergo meiosis
differentiate into elaters
single, elongate cells
Division anthocerotophyta: Hornwarts
usually hidden
100-150 named species
Gametophyte generation
as few as 3-4 protonema produced before this stage is established
always thin
ribbon or heart shaped
parenchymatous
not resistant to drying
winter annulas
appear in autumn months
grow in winter
die before sumer
numerous internal chambers
get invaded b Nostoc bacteria
a symbiotic relationship
Sporophyte generation
foot embedded in gametophore tissue
no setae or discrete sporangium
meristem
above the foot
continually produces new sporangium tissues
forms a long horn like cylinder
not known how closely related each division is
Formerly grouped in one division with three classes
