Transcript KINGDOM PLANTAE - Bio-Guru

KINGDOM PLANTAE
Chapters 29 & 30
Kingdom: PLANTAE
Characteristics
•Multicellular
•Mostly photosynthetic, contain chlorophyll
and other pigments
- some parasitic or carnivorous
•Cell walls made of cellulose
•Food stored as starch
•Subdivided into two main division –
Bryophytes (non-vascular plants) and
Tracheophytes (vascular plants)
•Approximately 261,849 Species
Plants evolved from multicellular green algae
Proof:
1.
Plants are multicellular, eukaryotic, photoautotrophs
like most algae
2.
Plants contain cellulose in cell walls, just like green
algae, brown algae and dinoflagellates
3.
Plants contain chloroplasts with chlorophyll a and b
like most algae
Charophytes – green algae that are the
closest relatives of plants
Belong to:
Phylum chlorophyta
Class Charophycea.
They are common pond dwellers.
Proof of Relation between charophyceans
and modern land plants
1. Cellulose-synthesizing
protein rosettes found in
the cells of both. In other
algae, these complexes
are linear.
2. There is more cellulose
present in the cell walls
of charophyceans and
plants than other algae
Proof of Relation between charophyceans and
modern land plants
3.
Peroxisomes of land plants and charophyceans contain special
enzymes to prevent damage from photorespiration. Other algae
do not have these enzymes.
4.
In pond charophytes, a layer of durable polymer called
sporopollenin keeps their zygotes from drying out during dry
spells. Spores of some land plants are also covered with
sporopollenin.
5.
The flagellated sperm of certain land plants (like mosses)
resemble sperm of charophyceans.
6.
The cytokinesis of land plants and charophyceans is identical –
the formation of a phragmoplast (a fancy name for the lining up of
the vesicles from the Golgi body).
7.
Both – nuclear DNA and chloroplast DNA of land plants and
charophyceans are closely related!
The Phragmoplast
The Move to Land
• The move to terrestrial environments
occurred in the Silurian period of the
Paleozoic Era (about 500 million rears ago)
• The new terrestrial plants were faced with
many new challenges as a result of the
relative lack of water present in terrestrial
environments.
A Dilemma for terrestrial plants
• Algae could get water, O2 / CO2
as well as other nutrients from
one single medium: The water
they resided in.
• Plants have to obtain their
requirements from 2 different
media: Air and soil
• Plants have evolved two
systems to deal with this: The
subterranean root system and
an aerial shoot system
The Challenges Also Include:
1. support of the plant against gravity,
2. finding and taking in water for metabolic
processes,
3. reproduction with motile gametes (algae have
swimming sperm)
4. greater variability and extremes of climate, and
5. spatial separation of nutrients.
6. Different groups of plants have dealt with the
problems created by lack of water in various
ways. These solutions will be discussed with each
group of plants where appropriate
Alternation of Generations
Female – ovule
Male – Pollen grain
Spores
• Spores are usually haploid and unicellular and are
produced for asexual reproduction
• Spores are produced by diploid sporophytes. They can
be dispersed by wind and germinate when they land in an
ideal location.
• When they germinate, they produce haploid
gametophytes.
• The haploid gametophytes produce haploid gametes
(sperm and egg)
• Sperm and egg fuse to give rise to a diploid sporophytes.
Alternation of generations
• Sporophytes – are the mature, green plants that we see all
around us, They are diploid.
– They produce haploid spores via meiosis.
– The haploid spores give rise to haploid gametophytes (sperm or egg
producing units).
• Gametophytes – they are multicellular reproductive parts of
a plant that are haploid.
– The female gametophyte is termed the megaspore which is located
inside the ovule
– The male gametophyte is termed the microspore which is located
inside the pollen grain.
• The haploid megaspore and microspores produce haploid
gametes (egg and sperm).
• When the sperm fertilizes the egg, a diploid sporophyte is
created.
Spores versus Gametes
• Spores are the units of asexual
reproduction, because a single haploid
spore develops into a new haploid
organism (a haploid gametophyte).
• By contrast, gametes are the units of
sexual reproduction, as two haploid
gametes need to fuse to create a new
diploid organism (a diploid sporophyte).
Homo vs. Heterosporous
• Homosporous – The sporophyte produces only
one type of spore which gives rise to one type of
gametophyte that is both male and female.
These gametophytes then produce both sperm
and eggs. Example: Ferns, Mosses
• Heterosporous – The sporophyte gives rise to
two different spores (Male - Microspore and
female - megaspore). Each gives rise to a
separate gametophyte (Male gametophyte –
pollen, female gametophyte – ovule). The
female gametophyte will produce eggs and the
male will produce sperm.
Kingdom Plantae cont’d
Phylum
Non-Vascular Plants
(Bryophytes)
Vascular, Seedless
Plants (Tracheophytes)
Vascular, “Naked” Seed
Plants
(Gymnosperms)
Vascular Flowering
Seed plants
(Angiosperms)
Common Name
Number of Species
HEPTOPHYTA
Liverworts
6,000
ANTHOCEROPHYTA
Hornworts
100
BRYOPHYTA
Mosses
PSILOTOPHYTA
Wisk Ferns
LYCOPHYTA
Club Mosses
SPHENOPHYTA
Horsetails
PTEROPHYTA
Ferns
CYCADOPHYTA
Cycads
100
GINKGOPHYTA
Ginkgo
1
CONIFEROPHYTA
Conifers
550
GNETOPHYTA
Gnetophytes
70
ANTHOPHYTA
Flowering Plants
235,000
TOTAL
261,849
9,500
13
1,000
15
9,500
Kingdom Plantae cont’d
Non-vascular Plants – Short, live close to the ground in moist soil. Produce
spores. No true leaves or roots.
Sometimes all these 3 non-vascular divisions are collectively called BRYOPHYTES
Division Heptophyta (Liverworts) 
 Division Anthocerophyta (Hornworts)
Division Bryophyta (Mosses) 
Need rainwater so flagellated sperm from antheridia can swim to the eggs in
the archegonia. MOSSES ARE HOMOSPOROUS – one spore type creates both
male and female gametophytes.
Origin of Vascular plants
• Life cycle with a Dominant sporophyte
(unlike mosses, where the gametophyte
generation is dominant)
• Tissue called Xylem conducts water and
minerals from root to rest of plant
• Tissue called Phloem conducts sugar from
leaves (source) to rest of plant (sink)
– Lignin in xylem and phloem walls in addition
to cellulose.
• True roots and leaves.
Kingdom Plantae cont’d
Vascular Seedless Plants – Produce spores for reproduction
Division Psilotophyta (Whisk Ferns) 
 Division Sphenophyta (Horsetails)
Division Lycophyta (Club Mosses)
Division Pterophyta (Ferns)
Like mosses, ferns have flagellated
sperm that rely on water to swim from
antheridium to archegonium
FERNS ARE HOMOSPOROUS
Another Fern Diagram
Kingdom Plantae cont’d
Vascular Seed Plants – Produce seeds for reproduction, sperm are encased in
pollen, but seeds are not encased in ovaries – Gymnosperms or “Naked seeds”
 Division Gnetophyta (Gnetophytes)
Lives in deserts
Family: Welwitschia
Division Cycadophyta (Cycads)
Kingdom Plantae cont’d
Vascular Seed Plants – Produce seeds for reproduction
(Also known as gymnosperms)
 Division Ginkgophyta (Ginkgos)
Oldest trees on Earth.
Existed during the time of
the dinosaurs.
 Division Coniferophyta (Conifers)
All evergreens: Firs, Cedars,
Junipers, etc.
Gymnosperms are heterosporous
Kingdom Plantae cont’d
Vascular Seed, Flowering Plants – Produce seeds for reproduction
Seeds encased in ovaries – Division Anthophyta or Angiosperms
Two types of flowering plants:
Monocotyledons
Dicotyledons
Perfect Flowers
Angiosperm Reproduction
Comparison of generations in Mosses, Ferns and
Flowering plants
Differences between ovule and pollen
 Male
gametophyte or pollen
(came from the male microspore)
(Later divides into 2 sperm cells)
 Female
gametophyte or ovule
(came from the female macrospore)
Ovule Structure
Ovules form in the ovary.
Each contains 8 haploid
nuclei, in 7 cells including :
1 egg nucleus
2 polar nuclei (in one cell)
3 antipodals
2 synergids
All nuclei are haploid (n)
Pollen Structure
• Pollen grains are formed in anthers. Each
contains:
– 1 Tube nucleus
– 1 generative nucleus that divides into 2 sperm
nuclei after the pollen lands on the stigma
Fertilization and seed Production
(pollen grain)
Fertilization
1. The tube cell creates a pollen tube which tunnels all the way through the
carpel and enters the embryo sac.
2. The synergids of the embryo sac burst the end of the pollen tube.
3. Meanwhile, the generative cell has followed the pathway digested by the
tube cell. Along the way it has divided to produce two sperm cells.
4. The two sperm cells exit the pollen tube and enter the ovule.
5. One sperm cell unites with the egg. This process is called syngamy (union
of gametes). This produces a diploid zygote. The zygote will divide and
grow and differentiate to become a new embryonic plant with root, stem,
and leaf. Ultimately it will become an adult plant.
6. The other sperm cell unites with the central cell. This is a second syngamy!
This produces a triploid endosperm cell (one from sperm and one each
from the two polar nuclei).
7. The endosperm cell divides to form a nutritive tissue inside the seed. It
accumulates nutrients from the mother plant and stores them away for the
developing embryo inside the seed. The nutrients are stored as starch,
protein, and/or oil.
After Fertilization
• The mature ovule becomes the seed. The seed contains the
embryo. The integuments become the seed coat that
surrounds the endosperm and embryo. The mature carpel
(and sometimes associated tissues) becomes the fruit.
Stamens and
Seed (Ovule)
Fruit (Ovary)
Seed germination of seeds
depends on imbibition – the
absorption of water from the soil,
due to the lower water potential in
the dry seed.
The radicle is the first
part of the embryo to
push out of the seed.
This will be the first
root. The hypocotyl is
the lower section of the
stem and the epicotyl
is the upper part or
actively growing part of
the stem .
Alpha-amylase is released by the outer coat of the endosperm, to breakdown
the starch stored in the endosperm – food for the growing seedling.
THE END