KINGDOM PLANTAE

Chapters 29 & 30

Kingdom: PLANTAEKingdom: PLANTAE

CharacteristicsCharacteristics

•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 – ovuleMale – 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

PhylumCommon Name Number of Species

Non-Vascular Plants(Bryophytes)

HEPTOPHYTA Liverworts 6,000

ANTHOCEROPHYTA Hornworts 100

BRYOPHYTA Mosses 9,500

Vascular, Seedless Plants (Tracheophytes)

PSILOTOPHYTA Wisk Ferns 13

LYCOPHYTA Club Mosses 1,000

SPHENOPHYTA Horsetails 15

PTEROPHYTA Ferns 9,500

Vascular, “Naked” Seed Plants(Gymnosperms)

Vascular Flowering Seed plants(Angiosperms)

CYCADOPHYTA Cycads 100

GINKGOPHYTA Ginkgo 1

CONIFEROPHYTA Conifers 550

GNETOPHYTA Gnetophytes 70

ANTHOPHYTA Flowering Plants 235,000

TOTAL 261,849

Kingdom Plantae cont’dNon-vascular Plants – Short, live close to the ground in moist soil. Produce Short, live close to the ground in moist soil. Produce

spores. No true leaves or roots.spores. No true leaves or roots.

Division Heptophyta (Liverworts)

Division Anthocerophyta (Hornworts)

Division Bryophyta (Mosses)

Sometimes all these 3 non-vascular divisions are collectively called BRYOPHYTES

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’dVascular Seedless Plants – Produce spores for reproduction

Division Psilotophyta (Whisk Ferns)

Division Lycophyta (Club Mosses)

Division Sphenophyta (Horsetails)

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’dVascular Seed Plants – Produce seeds for reproduction, sperm are encased in

pollen, but seeds are not encased in ovaries – Gymnosperms or “Naked seeds”

Division Cycadophyta (Cycads)

Division Gnetophyta (Gnetophytes)

Family: Welwitschia

Lives in deserts

Division Ginkgophyta (Ginkgos)

Division Coniferophyta (Conifers)

Kingdom Plantae cont’dVascular Seed Plants – Produce seeds for reproduction

All evergreens: Firs, Cedars, Junipers, etc.

Oldest trees on Earth. Existed during the time of the dinosaurs.

(Also known as gymnosperms)

Gymnosperms are heterosporous

Kingdom Plantae cont’dVascular Seed, Flowering Plants – Produce seeds for reproductionSeeds encased in ovaries – Division Anthophyta or Angiosperms

Two types of flowering plants:MonocotyledonsDicotyledons

Perfect Flowers

Angiosperm Reproduction

Comparison of generations in Mosses, Ferns and Flowering plants

Differences between ovule and pollen

(Later divides into 2 sperm cells)

Male gametophyte or pollen(came from the male microspore)

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 nucleus2 polar nuclei (in one cell)

3 antipodals2 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)

Fertilization1. 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)

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 .Seed germination of seeds

depends on imbibition – the absorption of water from the soil, due to the lower water potential in the dry seed.

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