Kingdom PlantaeKingdom Plantae

Characteristics of plantsAll Plants: Eukaryotic Multicellular AutotrophicUsed for Classification:

Pigments: chlorophyll, carotenoids, fucoxanthins, xanthophylls

Energy Storage: starches

Tissues: vascular/non for transporting H2O & nutrients

Structures: roots, stems, leaves

Life Cycles/Alternation of Generations:gametophytes = n, sporophytes = 2n

Reproduction: presence/absence of seed

presence/absence of fruit

PLANTLEAFperformsphotosynthesis

CUTICLEreduces waterloss; STOMATAallow gas exchange

STEMsupports plant(and may performphotosynthesis)

Surrounding watersupports the alga

ALGA

WHOLE ALGAperformsphotosynthesis;absorbs water,CO2, andminerals fromthe water

HOLDFASTanchors the alga

ROOTSanchor plant;absorb water andminerals from the soil (aidedby mycorrhizalfungi)

Characteristics of plants• Mainly terrestrial and sessile• Display an alternation of

generations.– sporophyte and gametophyte are

heteromorphic-the two generations look and develop differently from each other.

– In algae the gametophyte is dominant, in most plants the sporophyte is dominant.

• Sugars made via photosynthesis are used as a fuel source for growth and also stored as the complex carbohydrate starch.

• Cell walls are made of cellulose.• The Source of the Oxygen Produced by Photo

synthesis

• Photophosphorylation

• Tracing the Pathway of CO2

Alternation of Generations

• Unlike algae, plants have vascular tissue – It transports water and nutrients throughout the plant body

– It provides internal support– How is vascular tissue arranged differently in C3 and C4 plants?

Making the move to dry landRequired several evolutionary breakthroughs.What would be the key adaptations needed if you are going from an aquatic to a terrestrial existence?

Cooksonia

Modern angiosperm

Charophyte

Terrestrial Challenges & Adaptations

• Air offers no support to fight gravity.• Water is less available which results in dessication,

immotility of sperm, lack of absorption, problems with gas exchange and a need for conduction

• Nutrients and water are in soil, but CO2 and light are above ground.

• Protective covering to prevent dehydrationProtective covering to prevent dehydration

• Transport system for water & nutrientsTransport system for water & nutrients• Structural system for supportStructural system for support (woody tissue) (woody tissue)• Discrete organs- roots, stems, leaves & gametangia.Discrete organs- roots, stems, leaves & gametangia.• Protective covering for gametes & embryosProtective covering for gametes & embryos• Mechanism to allow sperm to get to eggMechanism to allow sperm to get to egg

Cladogram of the major plant groupsCladogram of the major plant groups4 Major Plant 4 Major Plant

Groups:Groups:

1.1. BryophytesBryophytesNonNonvascular Plantsvascular Plants

2.2. PteridophytesPteridophytes Vascular Plants Vascular Plants without Seedswithout Seeds

3.3. GymnospermsGymnosperms Vascular Plants Vascular Plants with Naked with Naked SeedsSeeds

4.4. AngiospermsAngiosperms Vascular Plants Vascular Plants with Seeds, with Seeds, Flowers, and Flowers, and FruitsFruits

Avascular Plants : Mosses, Hornworts Avascular Plants : Mosses, Hornworts & Liverworts& Liverworts

Life Cycle of a Moss

Seedless Vascular Plants : Ferns, Club Seedless Vascular Plants : Ferns, Club mosses, Horsetailsmosses, Horsetails and Whisk fernsand Whisk fernsNew evolutionary adaptations:New evolutionary adaptations:•Waxy cuticleWaxy cuticle•GametangiaGametangia

Features still absent in this group:Features still absent in this group:•No well developed vascular systemNo well developed vascular system•No support systemNo support system•Require water for sperm to swim to Require water for sperm to swim to eggegg

Cuticle: waxy covering on the surface of plant stems and leaves which prevents desiccation;Stoma (stomata): microscopic pore surrounded by guard cells in the epidermis of stems and leaves that allows gas exchange

Figure 29.11  The life cycle of a fern

Fern Life Cycle1, 2

• Ferns and other seedless plants once dominated ancient forests– Their remains formed coal

• Gymnosperms that produce cones, the conifers, largely replaced the ancient forests of seedless plants– These plants remain the dominant gymnosperms today

Seedless plants formed vast “coal forests”

• Sporangia in male cones make spores that develop into male gametophytes– These are the pollen grains

• Sporangia in female cones produce female gametophytes

A pine tree is a sporophyte with tiny gametophytes in its

cones

When do most plants reproduce? Why?•Reproduction and rearing of offspring require free energy beyond that used for maintenance and growth. Different organisms use various reproductive strategies in response to energy availability.

Egg (n)

1

HAPLOIDDIPLOID

Sperm (n)

Male gametophyte(pollen grain)

Female gametophyte (n)

Zygote(2n)

Seedcoat

Embryo(2n)

Seed

Sporophyte

Scale

Sporangium(2n)

Ovule

Integument

MEIOSIS

HAPLOIDPollen grains(malegametophytes)(n)

MEIOSIS Fertilization

Female conebears ovules.

2 Male cone producesspores by meiosis;spores develop intopollen grains

3 Pollination

4 Haploid spore cells inovule develop intofemale gametophyte,which makes egg. 5 Male gametophyte (pollen)

grows tube to egg andmakes and releases sperm.

6 Zygote developsinto embryo, andovule becomesseed.

7 Seed falls toground and germinates,and embryo grows into tree.

Life Cycle of a Conifer

• Most plants are angiosperms– The hallmarks of these plants are flowers– The angiosperm plant is a sporophyte with gametophytes in its flowers

• The angiosperm life cycle is similar to that of conifers– But it is much more rapid– In addition, angiosperm seeds are protected and dispersed in

fruits, which develop from ovaries

The flower is the centerpiece of angiosperm reproduction

STAMEN

Anther

Pollen grains

Stigma

Ovary

CARPEL

PETAL

SEPALOvule

HAPLOID

DIPLOID

Egg (n)

Ovule

Stigma

Pollengrain

Pollentube

Sperm

Fertilization

Seedcoat

Embryo(2n)

Seeds

Sporophyte

Ovary

Ovule

Pollen (n)

Meiosis

1 Haploid sporesin anthers develop

into pollen grains: male gametophytes.

2 Haploid spore in eachovule develops intofemale gametophyte,which produces egg.

3 Pollinationandgrowthof pollentube

4 Zygote(2n)

5 Seed

6 Fruit

7 Seed germinates,

and embryo grows into plant.

Food supply

Double Fertilization

Polyploidy in plants • common in plants, especially

in 30%-70% angiosperms, are thought to be polyploid.

• i.e. Species of coffee plant with 22, 44, 66, and 88 chromosomes suggesting ancestral condition (n) = 11 and a (2n) = 22, from which evolved the different polyploid descendants.

• Polyploid plants are larger, leading to created varieties of watermelons, marigolds, and snapdragons

•

Plant

Probable ancestral haploid number

Chromo#

Ploidylevel

domestic oat 7 42 6n

peanut 10 40 4n

sugar cane 10 80 8n

banana 11 22, 33 2n, 3n

white potato 12 48 4n

tobacco 12 48 4n

cotton 13 52 4n

apple 17 34, 51 2n, 3n

Origin of Polyploidy• Accident Doubling Plants, (vs

animals), form germ cells from somatic tissues. If the chromosome content of a precursor somatic cell has accidentally doubled (e.g., as a result of passing through S phase of the cell cycle without following up with mitosis and cytokinesis), then gametes containing 2n chromosomes are formed.

• Naturally occuring As the endosperm (3n) develops in corn (maize) kernels (Zea mays), its cells undergo successive rounds (as many as 5) of endoreplication producing nuclei that range as high as 96n.

• When rhizobia infect the roots of their legume host, they induce the infected cells to undergo endoreplication producing cells that can become 128n (from 6 rounds of endoreplication).

Polyploidy and Speciation • When a newly-arisen

tetraploid (4n) plant tries to breed with its ancestral species (a backcross), triploid offspring are formed. These are sterile because they cannot form gametes with a balanced assortment of chromosomes.

• However, the tetraploid plants can breed with each other. So in one generation, a new species has been formed.

• Fruits are adaptations that disperse seeds

The structure of a fruit reflects its function in seed dispersal

Types of Fruits• Simple Fruits: These fruit

types are produced by flowers containing one pistil, the main female reproductive organ of a flower.

• Aggregate Fruits: These fruits types are developed from flowers which have more than one pistils. They consist of mass of small drupes that develops from a separate ovary of a single flower.

• Multiple Fruits: These fruit types are developed not from one single flower but by a cluster of flowers.

• Accessory Fruits: These fruit types are developed from plant parts other than the ovary.

Types of fleshy fruits

True berry: have a soft epicarp and the mesocarp and endocarp is fleshly

Pepo: berry has an outer wall /rind that is formed from receptacle tissue that is fused to exocarp.

Hesperidium: have thick, leathery exocarp and mesocarp. They have a juicy, pulpy endocarp

Aggregate fruit: formed from

the development of

a number of simple carpels from a single

flower.

Multiple fruit: individual

ovaries from different

flowers get clustered together forming a

fruit.

Accessory fruit

Tomato, Eggplant, Chili pep, Grape, Cranberry,

Pumpkin, Gourd, Cucumber, Melon

Orange, Lemon, Lime, Grapefruit

Blackberry, Raspberry, Boysenberry

Pineapple, Fig, Mulberry, Hedge apple

Strawberry

There are fruits that are dry fruits and can be differentiated as dry dehiscent and dry indehiscent. Fruit types that contain seeds in a seedpod that opens up and releases the seeds are known as dehiscent fruits. Legume: Sweet pea, Beans, Peanut The indehiscent are those fruit types that do not have a seed pot that opens. Caryopsis: Wheat, Rice , Corn, Rye Nuts: The list of fruits under this type are: Walnut, Acorn

• Gymnosperms supply most of our lumber and paper

• Angiosperms provide most of our food – Fruits, vegetables, and grains

• Angiosperms also provide other important products– Medications, fiber, perfumes

Agriculture is based almost entirely on angiosperms

• Angiosperms are a major source of food for animals– Animals also aid plants in pollination and

seed dispersal

Interactions with animals have profoundly influenced angiosperm

evolution

Figure 17.13A-C

• 20% of the tropical forests worldwide were destroyed in the last third of the 20th century

• The forests of North America have shrunk by almost 40% in the last 200 years

Connection: Plant diversity is a nonrenewable resource

• Some plants in these forests can be used in medicinal ways

– More than 25% of prescription drugs are extracted from plants

Resources• Anatomy & Morphology of Plant

Organs• The Conquest of Land • Plant Evolution Tour• Identification of Major Fruits