Chapter 29

only red

What key traits appear in nearly all plants?

• reproduction: alternation of generations

• walled spores produced in sporangia

• growth: apical meristems

What is alternation of generations

Type of plant life cycle consisting of multicellular forms that gives rise to each other in turn.

What are the two multicellular generations in the plant life cycle?

Gametophyte (n) and sporophyte (2n).

What does the gametophyte produce, and by what process?

Haploid gametes (sperm and eggs, n) by mitosis.

What does the sporophyte produce, and by what process?

Haploid spores (n) by meiosis

what do spores develop into?

Gametophytes (n)

What does a fertilized egg (zygote, 2n) develop into?

a sporophyte (2n)

What is the plant life cycle called "alternation of generations?”

Because plants alternate between haploid gametophytes and diploid sporophytes, both multicellular.

The sporophyte produces spores in multicellular organs called….

sporangia

spore walls contain …… which makes them resistant to harsh environments

sporopollenin (structural integrity to spores)

Determinate growth

organism or part of an organism grows to a certain size and then stops

Indeterminate growth

organism or part of an organism continues to grow indefinitely, without a predetermined endpoint

Apical Meristems

Localized regions of cell division at the tips of roots and shoots

Primary growth (apical meristem)

tips of roots and shoots; length

Secondary growth (apical meristem)

thickening of the trunk and branches

Vascular cambium (secondary growth in apical meristem)

produces new layers of xylem and phloem

Cuticle

a waxy covering of the epidermis that reduces water loss

Stomata

pores that facilitate gas exchange between the outside air and internal plant tissues; close to decrease water loss

Ectomycorrhizae

• dense sheath around roots

• hyphae extend into the soil to increase nutrient absorption

Endomycorrhizae

• hyphae penetrate the root cells (arbuscules)

produce food through photosynthesis

Autotrophs

informal term for all nonvascular plants - liverworts, mosses, and hornworts

Bryophytes

club mosses and their relatives

Lycophytes

ferns and their relatives

monilophytes

Gymnosperms

seeds are not enclosed in chambers

Angiosperms

seeds develop inside chambers that originate within flowers

Bryophytes are represented today by three phyla of small, herbaceous (nonwoody) plants:

• Liverworts, phylum Hepatophyta

• Mosses, phylum Bryophyta

• Hornworts, phylum Anthocerophyta

(all require standing water for reproduction)

In bryophytes (mosses, liverworts, hornworts), which generation is dominant?

The haploid gametophyte is dominant - it is larger, longer-living, and supports the sporophyte.

Mass of green, branched, one-cell-thick filaments produced by spores

Protonema

What do Protonema do?

absorbs water and nutrients; forms “buds” that develop into gametophytes

Most bryophytes are constrained in….

height

Some moss species have …… that enable growth

conducting tissues

• remember: multicellular, but no vascular tissue

root-like structures that anchor gametophytes to the substrate

Rhizoids

Gametophytes can produce multiple …., structures that produce gametes

gametangia

Archegonia

female gametangia, produce a single nonmotile egg

• Gametophyte → Gametangia → Gametes

Antheridia

male gametangia, produce many motile sperm

• Gametophyte → Gametangia → Gametes

…… swim to the …… through a film of water in response to chemical attractants

Flagellated sperm, egg

• Antheridia to Archegonia

In bryophytes, where is the fertilized egg and resulting embyro retained?

within the archegonium

What is sexual reproduction limited by for bryophytes

• water availability

• proximity of male and female gametophytes

How does a sporangium (capsule) produce spores

meiosis

What is an ecological importance of moss?

help retain nitrogen in bare, sandy soil

Where are seedless vascular plants restricted to?

moist habitats where the sperm can swim to the egg

What are ferns and other seedless vascular plants characterized by

• Life cycles with dominant sporophytes

• Transport in vascular tissues called xylem and phloem

• Well-developed roots and leaves

• Spore-bearing leaves called sporophylls

In seedless vascular plants, are sporophytes or gametophytes dominant?

Sporophytes are larger and more complex (dominant) than gametophytes

Xylem does what

conducts most of the water and minerals and includes tube-shaped cells called tracheids

What are xylem strengthened by

a polymer called lignin

How are the cells of phloem tissue organized and what do they do

Arranged in tubes for transport of organic materials, such as sugar

Why are vascular tissue like xylem and phloem important

provides the structural support and long-distance transport needed for plants to grow tall

organs that anchor vascular plants into ground and absorb water and nutrients from soil

roots

What do leaves do

• increases surface area for light capture

• conducts most of the photosynthesis in plants

Two types of leaves

microphylls and megaphylls

What are microphylls

small, often spine shaped leaves with a single vein

• found only in lycophytes

What are megaphylls

larger leaves, with a highly branches vascular system

• found in all other plant groups

Sporophylls

modified leaves with sporangia

Clusters of sporangia on the undersides of fern sporophylls

sori

Most seedless vascular plants are…

homosporous

• one type of sporophyll and sporangium

All seed plants and some seedless vascular plants are….

heterosporous

• two types of sporophylls

• Megaspores - female gametophytes

• Microspores - male gametophytes