Chapter 25: Seedless Plants

BSC2011C Fall '25

Why do aquatic plants have it “easy”?

No desiccation, no structural support needed, protection from UV rays, gametes are transported through water and gametes/zygotes aren’t threatened with desiccation.

What are some advantages to terrestrial living?

Abundant sunlight, abundant CO2, no competition, no predators.

What are some disadvantages to terrestrial living?

Threat of desiccation, UV ray harm, need of structural support, reproduction is water dependent and zygote is water dependent.

What were the first terrestrial plant strategies?

Lived near water/humidity, tolerance of desiccation, remained small, developed mechanism against UV rays, and used natural selection.

What does sporopollenin do?

Protects spores/pollen from desiccation.

What is the alternation of generations life cycle?

Describes the life cycle of organisms that have multicellular diploid and haploid life stages;

1. sporophyte stage → makes spores

2. gametophyte stage → makes gametes

What does the apical meristem in roots and shoots do?

Allows vertical growth

What does the waxy cuticle on leaves and stem do?

Prevents desiccation

What does lignin in vascular tissues do?

Provides structural support

What are spores’ cell walls made of?

Sporopollenin

In humans, what kind of cellular body are our diploid and haploid stages?

Diploid Stage — Multicellular

Haploid stage — Unicellular

In plants, what kind of cellular body are our diploid and haploid stages?

Both are multicellular

In seedless plants, what does the haploid gametophyte stage produce?

Haploid gametes through mitosis

In seedless plants, what does the diploid sporophyte stage produce?

Haploid spores through meiosis

For seedless plants, what is the diploid stage?

Sporophyte

For nonvascular seedless plants, what stage is dependent on another stage?

Sporophyte stage is dependent on the gametophyte (n) stage

What does the sporophyte produce?

Sporangia

What is the sporangium structure made up of?

Sporocyte cells

Name the top and bottom structures

Sporophyte; Gametophyte

What do spores germinate into?

New haploid gametophyte plants

What are homosporous sporophytes?

Sporophytes that only make one type of spore

What do the spores from homosporous sporophytes germinate into?

Monoecious gametophyte

Are seedless plants mostly homosporous or heterosporous?

Mostly homosporous

What are heterosporous sporophytes?

Make two different types of spores

What are microspores?

Male spores

What are megaspores?

Female spores

What do microspores develop into?

Male gametophytes which only make male gametes

What do megaspores develop into?

Female gametophytes which only make female gametes

Are all seed plants heterosporous or homosporous?

Heterosporous

For seedless plants, what is the haploid stage?

Gametophyte

What does the gametophyte stage in seedless plants produce?

Gametangia through mitosis.

What is gametangia?

Structures that make haploid gametes through mitosis.

What are male gametangium called?

Antheridium

What do antheridium produce?

Sperm

How are sperm able to swim in water?

Flagella

What is the female gametangium called?

Archegonium

What do archegonium produce?

Eggs

After the fusing of the sperm and egg, where does the diploid sporophyte develop?

Inside the archegonium

What is meristem tissue made up of?

Undifferentiated cells

What special characteristic do apical meristems have?

They can develop into any type of cell

Where are apical meristems located?

Shoot tip and root tip of plants

How do apical meristems help the plant?

Allow for vertical upward growth and vertical downward growth

How does upward growth of the shoot help the plant?

Gives plants access to the sun

How does vertical downward growth of the root help the plant?

Gives plants access to water and minerals

How does wax in the epidermal tissue help the plant?

Prevents water loss and covers the surface of leaves and stem.

What are nonvascular seedless plants called?

Bryophytes

What type of plants are the most similar to the earliest terrestrial plants?

Bryophytes

What are nonvascular plants?

Contain no conductive tissue to transport water and products of photosynthesis

How do water and glucose move in nonvascular plants?

Diffusion

What is the dominant stage in bryophytes?

Gametophyte haploid stage

In bryophytes, what is the dependent stage?

Sporophyte diploid stage

What are the three types of bryophytes?

Liverworts, hornworts, mosses

What is the bryophyte structure?

Nonvascular, thallus and rhizoids, very small, water-dependent fertilization, dominant gametophyte stage

What do sporophytes do to gametophytes in bryophytes?

Remain attached to and nutritionally dependent on the gametophyte

Where do gametangia grow from (in bryophytes)?

Thallus

How do archegonia/antheridia produce eggs/sperm?

Mitosis

What does fertilization in a bryophyte result in?

Diploid zygote

Where do diploid zygotes grow in bryophytes?

Archegonia (sporophyte stage)

What do sporangia produce?

Sporangia produce haploid spores via meiosis

What is the dominant stage in vascular seedless plants?

Sporophyte diploid stage

In vascular seedless plants, what stage is dependent?

Gametophyte stage is dependent on sporophyte stage

How do conductive vascular tissue help the plant?

Allows the plant to transport water, food, minerals and nutrients, and allows plants to grow tall

What does lignin in the xylem do for the plant?

Provides strength and structural support

How do roots in vascular seedless plants help the plant?

Anchors the plant and allows it to absorb water and nutrients from soil

How do leaves help vascular seedless plants?

Increased surface area for photosynthesis

What are microphylls?

Spine-shaped leaf with one unbranched vascular vein

What are megaphylls?

Large leaf with unbranched vascular system

What are sporophylls?

Modified leaves with sporangia

What do sporangia contain?

Sori and strobili

What are sori?

Clusters underneath the leaf of a fern sporophyll

What are strobili?

Cone-like structures formed from sporophylls

What are examples of vascular seedless plants?

Lycopodiophyte and Monilophytes

In vascular seedless plants, how do male gametes move?

They swim, fertilization is water-dependent

Zygotes in vascular seedless plants are…

independent and dominant

Spores in VSPs germinate to what?

Haploid gametophytes