Chapter 30 Chapter 30

Plant diversity continuedPlant diversity continued

Bryophytes Bryophytes (mosses, liverworts, hornwarts)(mosses, liverworts, hornwarts)

Mosses Liverworts

Hornworts

Homosporous vs. Heterosporous Homosporous vs. Heterosporous alternation of generationsalternation of generations

HOMOSPOROUS

The sporophyte’s sporangia

HETEROSPOROUS

Single type of spore Bisexual gemetophyte

Eggs

Sperm

Megaspore

Microspore

FemaleGametophyte

MaleGametophyte

Eggs

Sperm

The sporophyte’s sporangia

Bryophytes are non-vascular plantsBryophytes are non-vascular plants

The Gametophyte is the dominant generation.The Gametophyte is the dominant generation.

The bryophyte sporophyteThe bryophyte sporophyte The sporophyte has The sporophyte has

specialized structures specialized structures that produce spores that produce spores called called Sporangia.Sporangia.

Pteridophytes: The first seedless Pteridophytes: The first seedless vascular plants (Ferns)vascular plants (Ferns)

Have lignified Have lignified xylem tissue so xylem tissue so they can grow they can grow taller than mosses.taller than mosses.

The dominant The dominant generation is the generation is the Sporophyte Sporophyte In In Pteridophytes, Pteridophytes, sporophyte is sporophyte is branched and branched and independent of the independent of the gametophyte.gametophyte.

Gametophyte

The Seeded Plants: Gymnosperms The Seeded Plants: Gymnosperms and Angiosperms and Angiosperms

Continued reduction of the gametophyteContinued reduction of the gametophyte The advent of the seedThe advent of the seed The evolution of pollenThe evolution of pollen

QUESTION: Why is the QUESTION: Why is the gametophyte reduced in size and gametophyte reduced in size and

is more associated with the is more associated with the mature, dominant sporophyte?mature, dominant sporophyte?

Gymosperms and Angiosperms Gymosperms and Angiosperms continued to reduce the gametophyte continued to reduce the gametophyte

generationgeneration

Delicate gametophytes (structures that produce Delicate gametophytes (structures that produce the delicate gametes) are reduced and develop the delicate gametes) are reduced and develop within the sporophyte. WHY?? within the sporophyte. WHY?? Protection Protection from environmental stresses.from environmental stresses.

In seeded (gymnosperms and angiosperm) In seeded (gymnosperms and angiosperm) plants the gametophyte is microscopic.plants the gametophyte is microscopic.

The evolution of the seeds The evolution of the seeds

Important to disperse your youngImportant to disperse your young Recall that spores (n) develop into gametophytes Recall that spores (n) develop into gametophytes

which produce gametes which produce gametes Spores are single celled Spores are single celled and have a thick coat and have a thick coat can resist harsh can resist harsh environmental conditionsenvironmental conditions

Seeds (2n) Seeds (2n) multicellular and more complex than multicellular and more complex than Spores (n)Spores (n) Seeds have an embryo and nourishment Seeds have an embryo and nourishment in the form of the female gametophyte or in in the form of the female gametophyte or in angiosperms, called endosperm. All seeded plants are angiosperms, called endosperm. All seeded plants are heterosporousheterosporous

From Ovule to SeedFrom Ovule to Seed

Pollen: Eliminated the liquid water Pollen: Eliminated the liquid water for fertilization.for fertilization.

Megasporangium is to ovuleMegasporangium is to ovule (Megasporangium produces the megaspore (Megasporangium produces the megaspore inside the ovule inside the ovule female gametophyte female gametophyte egg)egg)

ASAS Microsporangium is to pollenMicrosporangium is to pollen

(Microsporangium produces the microspore (Microsporangium produces the microspore pollenpollen male gametophyte male gametophyte Sperm)Sperm)

Advantage of Pollen Advantage of Pollen

Very resistant to environmental conditionsVery resistant to environmental conditions Can travel far (along the wind)Can travel far (along the wind) By bringing airborne pollen together with By bringing airborne pollen together with

ovules anchored in the archegonium of the ovules anchored in the archegonium of the female gametophyte female gametophyte This adaptation lead to This adaptation lead to great success on landgreat success on land

THE THE GYMNOSPERMSGYMNOSPERMS The production of naked seeds usually in The production of naked seeds usually in

conescones

Life Cycle of the Pine is a great example Life Cycle of the Pine is a great example of the reduction of the gametophyte in of the reduction of the gametophyte in

seeded plants.seeded plants.

Figure 30.9 The life cycle of a pine (Layer 1)Figure 30.9 The life cycle of a pine (Layer 1)

Figure 30.9 The life cycle of a pine (Layer 2)Figure 30.9 The life cycle of a pine (Layer 2)

Figure 30.9 The life cycle of a pine (Layer 3)Figure 30.9 The life cycle of a pine (Layer 3)

Angiosperms: Flowering plantsAngiosperms: Flowering plants

Two main classes; Monocots and DicotsTwo main classes; Monocots and Dicots Refinements in vascular tissue : Xylem tissue Refinements in vascular tissue : Xylem tissue

has tracheids like gymnosperms. Angiosperms has tracheids like gymnosperms. Angiosperms have additional Xylem cells called Vessel have additional Xylem cells called Vessel Elements.Elements.

Use of an attractor to ensure less random and Use of an attractor to ensure less random and wind dependent pollination wind dependent pollination

Monocots vs. DicotsMonocots vs. Dicots

Vessel elements in Angiosperm Vessel elements in Angiosperm XylemXylem

Structure of a flowerStructure of a flowerFemale portions (includesMegaspores and female gametophyte and ovary)

Male portions (includesMicrospores and male gametophyte)

Example: SAFFRON the most Example: SAFFRON the most expensive spice on the planetexpensive spice on the planet

Comes from the stamens of the male crocus Comes from the stamens of the male crocus plant.plant.

The cost per gram of the best saffron is more than that of gold! GOLD = $13.50/gram

The Rhodora On being asked, whence is the flower.

In May, when sea-winds pierced our solitudes,I found the fresh Rhodora in the woods,

Spreading its leafless blooms in a damp nook,To please the desert and the sluggish brook.

The purple petals fallen in the poolMade the black water with their beauty gay;

Here might the red-bird come his plumes to cool,And court the flower that cheapens his array.

Rhodora! if the sages ask thee whyThis charm is wasted on the earth and sky,

Tell them, dear, that, if eyes were made for seeing,Then beauty is its own excuse for Being;Why thou wert there, O rival of the rose!

I never thought to ask; I never knew;But in my simple ignorance suppose

The self-same power that brought me there, brought you.

Ralph Waldo Emerson

The Rhodora On being asked, whence is the flower.

In May, when sea-winds pierced our solitudes,I found the fresh Rhodora in the woods,

Spreading its leafless blooms in a damp nook,To please the desert and the sluggish brook.

The purple petals fallen in the poolMade the black water with their beauty gay;

Here might the red-bird come his plumes to cool,And court the flower that cheapens his array.

Rhodora! if the sages ask thee whyThis charm is wasted on the earth and sky,

Tell them, dear, that, if eyes were made for seeing,Then beauty is its own excuse for Being;Why thou wert there, O rival of the rose!

I never thought to ask; I never knew;But in my simple ignorance suppose

The self-same power that brought me there, brought you.

Types of fruit produced by Types of fruit produced by angiospermsangiosperms

Simple Fruits Single ovary, one flower

Aggregate Fruits Many ovaries, one flower

Multiple Fruits Many ovaries, clustered flowers

Life cycle of an angiospermLife cycle of an angiosperm

Note that the egg and the female Note that the egg and the female gametophyte become fertilized.gametophyte become fertilized.

The fertilized egg develops into the embryo The fertilized egg develops into the embryo which then develops into the mature which then develops into the mature sporophyte plant.sporophyte plant.

The fertilized gametophyte develops into the The fertilized gametophyte develops into the food (endosperm) for the developing embryo food (endosperm) for the developing embryo in the seed.in the seed.

Why double fertilize both egg and Why double fertilize both egg and female gametophyte?female gametophyte?

To ensure synchronous food source for a To ensure synchronous food source for a viable embryo.viable embryo.