PART 1 - CHAPTER 1 - CELL THE FUNDAMENTAL UNIT OF LIFE
Bryophytes :Amphibians of Plant Kingdom
1.
2. Bryophytes are among the simplest of the terrestrial
plants.
Lack complex tissue system.
Most of them are 2–5 cm tall or others less than 10 cm
long.
Commonly grow in damp, humid and shaded localities.
widely distributed throughout the world.
They are called amphibians of the plant kingdom
because they can live in soil but are dependent on
water for sexual reproduction.
3. The plant body is thallus-like
and prostrate or erect.
The body is attached to the
substratum by rhizoids.
They lack true roots, stem or
leaves.
They may possess root-like,
leaf-like or stem-like
structures.
4. The main plant body of the bryophyte is haploid(n).
It produces gametes, hence is called a gametophyte.
The sex organs in bryophytes are multicellular.
• Antheridium
• Produces
antherozoids
Male
sex
organ
• Archegonium
• produces egg
Female
sex
organ
5. Antherozoids are released into water and come in
contact with archegonium.
Egg (n) + Antherozoid (n) = Zygote (2n)
Zygotes grows into sporophyte.
The sporophyte is not free-living but attached to the
photosynthetic gametophyte and derives
nourishment from it.
Some sporophytes undergo meiosis, a reductional
cell division, to produce haploid spores.
Spores germinate to produce gametophyte.
6. 1. Ecological importance in succession - pioneers in
establishing vegetation in the barren rocks.
2. Prevent soil erosion
3. Provide food - Some mosses provide food for
herbaceous mammals, birds and other animals
4. Good Packing material – Sphagnum used to pack
bulbs, cuttings and seedlings for shipment
5. Used in seed beds and green houses.
6. Source of fuel - Sphagnum provide peat which is a
potential source of coal and used as fuel.
7. Absorbent bandages - Sphagnum plants are slightly
antiseptic and possess superior absorptive power.
8. liverworts are small, less than 10 cm
long thallus body.
The thallus is dorsiventral and
closely appressed to the substrate.
They have rhizoids, flattened stems
with overlapping scales or leaves.
They usually grow in moist, shady
habitats such as banks of streams,
marshy ground, damp soil, bark of
trees and deep in the woods.
The leafy members have tiny leaf-
like appendages in two rows on the
stem-like structures.
e.g., Marchantia.
9. 1. Fragmentation
2. Gemmae
Marchantia produce special
structures on their dorsal
structures called gemma cups.
Gemma cups give rise to very
tiny, lens shaped bodies called
gemmae.
The gemmae become
detached from the parent body
and germinate to form new
individuals.
10. Male and female sex organs
are produced either on the
same or on different thalli.
The male gametes are called
antherozoids.
The female gametes are
called archegoniophore.
Antherozoid reach to the
archegonia tip with the help
of water and gets fused with
egg and zygote is formed.
Male thallus, Marchansia
Female thallus, Marchansia
11. The zygote undergoes cell
division during development and
forms sporophyte.
The sporophyte is differentiated
into a foot, seta and capsule.
The capsule is surrounded by a
layer called jacket.
After meiosis, spores are
produced within the capsule.
These spores germinate to form
free-living gametophytes.
12.
13. Mosses are small nonvascular
bryophyta.
They grow in dense green clumps or
mats, often in damp or shady
locations.
They have root-like multicellular
rhizoid.
They have haplo-diplonts: haploid (n)
and diploid (2n) life forms alternate to
each other.
It’s predominant stage of the life cycle
is gametophyte. Funaria
14. Gametophyte consists of two stages.
Protonema stage develops directly from a spore.
It is a creeping, green, branched and frequently
filamentous stage.
Leafy stage develops from the secondary protonema as
a lateral bud.
Gametophyte
Protonema stage Leafy stage
16. Antherozoids (n) + Egg cells (n) =
Zygote (2n)
After fertilisation, the zygote
develops into a sporophyte,
consisting of a foot, seta and
capsule.
The sporophyte consists of three
structures:
i) Foot - anchors it to the
gametophyte and helps to transfer
water and nutrients from the
gametophyte.
ii) Seta - a long erect stalk
iii) Capsule - produce spores
Spores are formed after meiosis.
17. Polytrichum
Sphagnum
When spores fall onto
ground, it may germinate into
a branching, threadlike
filamentous protonema.
Buds from the protonema
grow into leafy male or
female gametophytes
Examples :
Funaria,
Polytrichum and Sphagnum