Chapter 19 -- SEEDLESS VASCULAR
PLANTS
Major themes: Upon
development of true vascular tissue, plants became anatomically complex, developing true roots, stems, and leaves.
The gametophyte became much reduced in size, and the sporophyte became more visible and longer lived, dominating
the life cycle. Sperm of seedless vascular plants still require water
in order to swim to the egg. Their sporangia may be clustered in
cones called strobili.
I.
Evolution of vascular plants (seedless
and
seed producing):
A.
To prevent desiccation:
1.
Evolved spores with thick, protective
walls & developed a cuticle
The cuticle is waterproof and consists
of cutin + waxes
2.
stomata for – _______________________________________
B.
Other early adaptations:
1.
conducting systems (xylem &
phloem) -- transport _____________
2.
Incorporation of lignin in cell
walls of supporting & water-_________
3.
true roots, stems, & leaves
4.
reduction of gametophyte stage;
_____________ dominates
5.
seeds (= embryonic sporophyte)
-- seed-producing plants only
C.
Direct ancestor -- perhaps a multicellular
green alga
=
Oldest
known fossil --
Cooksonia (~ ___________ yr. ago)
D.
Became numerous and diverse by
the Devonian period
(_____________________
million years ago).
E.
9 divisions (~ _______________
species )
II.
General features of seedless vascular
plants:
A.
All of the above, except they are
seedless
B.
flagellated sperm -- must have
_________________________
C.
Sporophyte is __________________________________;
Sporophyte
is often __________________
D.
Sporophyte and gametophyte are
nutritionally independent of each other.
The gametophyte is often short
lived.
Gametophytes are photosynthetic
in ferns and horsetails, but in club mosses and whisk ferns they are saprophytic.
E.
archegonium ---> 1 egg; antheridium
--> several sperm
Life cycle resembles that of ___________________________
III. Plant body organization (all vascular plants):
A. Early
sporophyte was dichotomously branched (evenly forked)
--
lacked leaves & roots. Instead
they had:_____________________________________________
B.
Later, organ systems evolved:
1.
root system -- __________________________________________________
2.
shoot system --stems & leaves
(photosynthesis, conduction of water _______
C.
Three tissue systems (continuous
-- occur in all organs):
1.
dermal
= outer, protective covering
2.
vascular
= conductive tissue (______________); embedded in ground tissue
3.
ground tissue (mesophyll, cortex, etc.)
D.
Primary & secondary growth:
1.
primary
-- occurs near tips of roots & stems; initiated by apical meristems; involved in the extension of the plant
body; primary plant body.
Occurs in all ______________________
2.
secondary
-- thickens stems & roots; produced by lateral
meristems (such as the vascular
cambium); secondary plant body.
Occurs in woody plants,
such
as __________________________ & ancient seedless vascular plants.
E.
Conducting cells:
1.
tracheid (xylem) = elongate
tracheary element with tapering ends; the first water-conducting
cells; the only type in most plants except __________; lignified walls
2.
vessel
(xylem) = the more specialized water-conducting cell of angiosperms; not present in ________________________________________________
3.
sieve element (phloem) -- soft walled;
F. Stele
= arrangement of vascular tissues (plus pith, if present) in the central cylinder of the stem & root of the
primary body
1.
protostele
-- ________________ type: solid strand of vascular tissue
(no _____); found in roots of most plants (except
some monocots)
Examples:
Found in stems of Psilotum
& Lycopodium
2.
siphonostele -- has a pith (ground tissue) in the center
& surrounded by
________________________________________________________
Stem
may have leaf gaps -- placec where vascular strand is missing
from the siphonostele; associated with leaf
traces -- vascular tissue that
enters leaves
Examples:
Typically found in ferns &
woody dicot stems.
3.
eustele
-- has discrete _______________________________________
Examples: Typically found in horsetails and ferns and
in the stems of some angiosperms (herbaceous dicots & monocots).
IV.
Origin of roots and leaves:
Note -- the stem evolved first
as the axis of the plant.
A. Roots
are fairly simple & primitive in structure;evolved from
underground stems (rhizomes) &
retained a protostele
B.
Leaves = primary lateral appendages
of the stem
1.
Arise as protuberances (or primordia)
from the apical meristem
2.
Two major kinds:
a.
microphylls -- relatively small; contain a ______ strand
of vascular tissue
Associated with stems having protosteles;
found in lycophytes
Their
leaf traces are not associated with leaf gaps.
Probably evolved as outgrowths
of the main axis of the plant.
b. megaphylls
-- larger; have a complex system of veins
Associated with stems having siphonosteles
or eusteles;
found
in most plants.
Their
leaf traces are associated with leaf gaps.
V.
Reproduction in vascular plants
Recall they are all
oogamous and have the alternation of heteromorphic
generations life
cycle.
A. Early vascular plants are homosporous -- produce only one kind of spore ---> typically produce _________________l gametophytes
Examples:
psilophytes, horsetails, some lycophytes,
& most ferns
Gametophytes
develop outside the spore wall.
B. More
advanced vascular plants are heterosporous – produce 2 types of spores (in 2 kinds of
sporangia):
microspores (from ______________) -- produce male gametophytes
megaspores (from
megasporangia)
-- produce female gametophytes
Gametophytes
develop within the spore wall.
Examples: Selaginella,
some ferns, all gymnosperms and angiosperms
C.
Sporangia may be single or aggregated
into a cone (= strobilus)
A.
Flourished during Devonian; extinct
by 360 million yr ago
B.
General characteristics:
1. No leaves & no roots; homosporous.
2.
Dichotomously branched
C.
Phylum Rhyniophyta -- the earliest known vascular plants
(~ 420 million years ago)
e.g., Cooksonia & Rhynia
D.
Phylum Zosterophyllophyta
Probably
the ancestors to the lycophytes.
E.
Phylum Trimerophyta
Larger
plants as compared with plants in the previous 2 divisions and probably were the ancestors to _____________________________________________
VII. 4
extant phyla of seedless vascular plants:
A.
Phylum Psilotophyta (only
2 genera)
1.
Psilotum
(whisk fern) -- occurs in FL, LA, TX, AZ, Hawaii,
& Puerto Rico
The only living vascular plant
that lacks both ________________!
a. Has dichotomously branched stem with small outgrowths;
underground rhizome with rhizoids; sporangia borne on the ends of short, lateral branches; stem has a __________________________
b.
Has bisexual, subterranean gametophytes
2.
Tmesipteris -- epiphyte; occurs in the South Pacific; has
leaflike appendages
B.
Phylum Lycopodophyta (club mosses)
1. 3 orders (3 _____________)
of living species; all
are herbaceous, & sporophyte has microphylls, stems, and roots
2.
Lycopodiaceae -- club mosses (e.g.,
Lycopodium);
evergreen
a. sporophyte has branching rhizome from which
aerial branches & adventitious roots emerge; stem & roots have protosteles
b.
microphylls are __________ arranged
c. homosporous, & sporangia are borne on fertile
microphylls called sporophylls.
In many species, sporophylls are
grouped into ___________
3.
Selaginellaceae -- Selaginella
(the only living genus)
a.
Leaves occur in 2 ranks
b.
heterosporous; both kinds of spores
occur in the same strobilus
c.
Has a ligule (_________ growth)
near base of upper surface of
each microphyll & each sporophyll
d.
stem and root have ______________________
4.
Isoetaceae -- Isoetes
(the only living genus)
C.
Phylum Equisetophyta -- horsetails or scouring rushes
(e.g., Equisetum -- the only living genus).
1.
appeared during Devonian. During
the late Devonian and
Carboniferous
periods, __________________________________
2.
Equisetum
sporophyte is herbaceous.
Occurs in moist places, along streams,
along edges of woods:
a.
conspicuously ________ stems,
small scalelike leaves, rough texture
b. leaves are whorled at nodes, & branches
(if present) occur laterally at the nodes, alternating with leaves
c.
internodes are ribbed and contain
siliceous deposits.
Adventitious roots arise at the nodes of the rhizome.
d.
perennial; _________________;
spores ----> sporangia ---->
sporangiophore ----> strobilus
e.
gametophyte is the size of a pinhead,
is green & freeliving,
D.
Phylum Pteridophyta -- ferns (~ 12,000 species; largest group of
vascular plants other than flowering plants).
1.
abundant since Carboniferous period
(360 million yr ago)
2.
tropical & also temperate in
distribution.
Greatest diversity in tropics (~
one-third of these are epiphytes).
3.
sporophyte has megaphylls, stems,
adventitious roots, rhizomes;
sporangia are borne on fertile
leaves or a fertile segment.
4.
most are homosporous; 2 groups
of water ferns are heterosporous
5.
important morphological features:
a.
frond =
b.
fiddlehead =
c.
prothallus =
6.
Order Ophioglossales (eusporangiate)
-- grape ferns and adder's tongues.
(e.g., Botrychium & Ophioglossum).
7.
Order Pteridales -- most ferns
belong to this order.
Leptosporangiate.
Homosporous.
Rhizome
bears new sets of fronds each year; often these are compound & have leaflets called ______________
Sporangia
-- on lower surface of fronds, on specially modified leaves, or on separate stalks;
often occur in clusters called
sori
(singular = sorus)
Sorus
may or may not be covered by indusium;
indusium
is _____________________
8.
Order Marsileales & Salviniales
-- water ferns
Marsilea
-- rhizome grows in mud, leaves often float
Salvinia
(duckweed) --
entire plant floats & is tiny
Azolla
--
also tiny and entire plant floats