Download Chapter10 Pteridophyta

Chapter10 Pteridophyta
Main teaching content: the characteristic of Pteridophyta, the morphosis and life
cycle of pteris's sporophore and gametophytic, their economical significance, and
Pteridophyta's class and its origin.
Nnode and nodus: the characteristic of Pteridophyta,the morphosis and life cycle of
pteris's sporophore and gametophytic.
Teaching style: teach 2 classes using multimedia .Observe and identify plants in the
extracurricular practice.
First, Pteridophyta's characteristic
Pteridophyta is also called ferns, belong to vascular plants, still breed on spores.
It’s a group which between bryophyte and spermatophyte.
Characteristic:
1、 It has many spores, real differentiation of rhizel and frond. The roots are all real
except very few crude species, but the main root can’t usually be adventitious
root.
2、 The fronds can be divided to sporophyll and trophophyll. We call those fronds
that can produce sporange and spore trophophyll homofronds.Some
Pteridophyta’s trophophyll and sporophyll are inseparate. They have whole
functions of organisms,and also can produce spores who have the same shape.We
call those pteridophyta homomorphic leaf; to the contrast, one plant who has two
kinds of different shapes and functions is called heteromorphic leaf.
3、 The biggest difference among Ferns ,bryophytes and other plants is that there is
apparente differentiation of vascular inside spores; the main components of
xylem are tracheid and xylem parenchyma, the main components of phloem are
sieve cell and phloem parenchyma. So,we can see that the function and efficiency
of ferns which can transport mineral salt and nutrient substance are
increased.This is very important for ferns to adapt the terrestrial environment .
4、 Spore cluster and spore
In the microphyll type of ferns, such as equisetum
drilgrass, sporangium only borns on every sporophyll’s leaf axil, and usually
many spores closely or focus on the top of branches, becoming ball or spike,
which we call them strobil or sporophyll spike.Anpther macrophyll type
ferns,many sporangium buildup sori or sporangium of different shapes, they born
on the sporophyll’s back or at the bridge of back.
5、 Gametophyte
Pteridophyta’s gametophyte is also called prothallium, they
are all small ,they have simple structure and short life cycle,and are all produced
by spore germination .Most pteridophyte’s gametophytes born on the surface of
wet soil,they have dorsiventral green pedalium, can live alone. On the ventral
aspect of gametophyte, there are many monocellular rhizoid, antheridium and
archegonium are all born on the ventral aspect of gametophyte. The antheridium
is out of body surface,and the archegonium is involved in the tissue of
gametophyte, only transverse part is exposed. In the presence of water, sperm-egg
fusion---zygote---nondormancy becoming embryo---sporophyte .
6、 Life history: apparente alternation of generations.asexual generations are
sporophytes that have diplochromosome.They can live longer. There are many
sporangiums on them ,in which sporoblast can form haplochromosomal spore(n)
by meiosis.The spores is spreading ,sprouting in proper environment,called
prothallium.Prothallium is samaller .It has short life cycle, antheridium and
archegonium on the dorsal aspect, producing sperm and spawn everywhere. The
sperm has many flagellums, goes inside the archegonium by water, binds with
spawn to synthesise zygote (2n), which develop to embryo and become spore that
can live alone.
Notable characteristic of Pteridophyta’s life cycle:
(1) spores become developed, gametophyte degenerate
(2) both of spore and gametophyte can live alone, antherid is called antheridium,
female organ is called archegonium
(3) the process of fertilization depends on water
Second, classfication of pteridophyte(accord to Renchang Qing’s classification
system):
Psilophytina、Lycophytina、Isoephytina、Sphenophytina、Filicophytina
(A)Psilophytina
Spore has only rhizoid, leaf is microphyll, stem dichotomous branches many
times, sporangium is born close to the top of sporophyll, homospory, monoecism,
spermatozoid in spiral shape, has many flagellums.
(B) Lycophytina
Spore has differentiation of root、stem and leaf; leaf is microphyll: only one
midrib, no folial gap; sporangium develops to strobile and sporophyll spike;
homospory or heterospory.
(C) Isoephytina
Born beside water or at the botom of water, leaf is thin and long like chive, grow
thickly on the short branch’s stem, heterospory, spermatozoid has many flagellums.
(D) Sphenophytina
Stem has apparente node and internode, leaf is small scale shaped, sporangium is
born on the top of branch, peitate, homospory, spermatozoid has many flagellums.
(E) Filicophytina
Separate criteria: according to the location, morphosis and developmental way
and sequence of sporangium. We separate Filicophytina into three class:
Eusporangiopsida: Sporangium has thick wall, is composed of several layers of
cells. Sporangium origin from a group of cells: Ophioglossales and Angiopteriales
Protoleptosporangiopsida: The wall of sporangium is composed of one layer of
cells. The sporangium origin from one or a group of cells, such as Osmunda vachellii
Hook.
LePtosporangiopsida: The sporangium is composed of one layer of cells.It
origins from one cell.
Represental plants:
Marsilea: hydric or, leaf has long stipe, four leaflets are born on the petiolar top.
The petiole is soft; leaf blade can float with water. When breeding, it produce
ambisexual sporocarp, endogenate sori, and micro- or macro-sporangium.
Macrosporangium has only one macrospore. Microsporangium has many microspores.
Macro- and micro-sporangium locate on the colloid. Sporocarp become mature,the
colloid expansions after sop and then stretch out of sporocarp, at the same time also
bring the sporangium out of the wall of fruit.
Azolla imbricata: also called azolla, water fern. Leaf is arranged like watt on the
stem, it has no stipe, split deeply into upper and down valves. The upper valve floats
on the water, operate photosynthesis. The hypovalva is born in the water, has no
pigment. The upper valve’s interior gap has colloid, and symbiosis with anabena.
Sporocarp is heteromorphosis, which can separate into macrospore and microspore.