Chapter 30

Antheridium

Structure that produces sperm, develops on the gametophyte

Plant and green algae similarity

cellulose cell walls chlorophylls a & b (in plastids) starch = storage unit cells w/ 2 anterior flagella

Moss sporophyte generation

dependent on gametophyte for nutritionf

Archegonia

female gametangia that bears a single egg

phloem

food is carried by

Moss gametophyte generation

photosynthetic

Homospory

production of only one type of spore as a result of meiosis -characteristic of bryophytes, horsetails, whisk ferns, and most ferns and club mosses

yes

Are ALL seed plants heterosporous?

liverwort gemmae

Asexual reproduction Little cups with tiny ...inside, dispersed by drop of water

Plant and algae differences

Land plants ... -Have multicellular haploid and diploid stages -Trend toward more diploid embryo protection -Trend toward smaller haploid stage

Archegonium

structure in plants that produces eggs

Bryophytes

- *seedless, non-vascular plants* - only living nonvascular plants - typically small to allow for diffusion of essential materials - *Only* plants with a *dominant gametophyte* generation - sporophytes remain permanently attached - Closest living descendants of the first land plants - require water for sexual reproduction - nontracheophytes - Mycorrhizal associations with fungi for water uptake - Gametophyte - conspicuous and photosynthetic Sporophytes - small and dependent - 25,000 species

Chlorophytes

- Never made it to land

Charophytes

- Sister to all land plants - together with land plants referred as streptophytes - do not have multicellular haploid and diploid stages, plants do

Diplontic

- diploid dominant - ferns, gymnosperms, angiosperms

Ferns & relatives (Phylum Pteridophyta)

- dominant sporophyte generation - *rhizome* ---> horizontal underground stem - true roots - all form antheridia and archegonia - all require water for flagellated sperm - Mostly terrestrial plants with a dominant sporophyte generation and *true roots* - gave rise to 2 clades: Whisk ferns and horsetails - both phases are photosynthetic - largest group of seedless vascular Fern life cycle differs from that of a moss -Much greater development, independence, and dominance of the fern's sporophyte -Gametophyte lacks vascular tissue SOME HETEROSPOROUS

gametophyte

- haploid (n) -gamete-producing generation, which alternates with the diploid (2n) sporophyte. - gametes by mitosis -haploid sperm and egg fuse to form zygote ---> grows and becomes first cell of sporophyte generation

Haplontic

- haploid dominant - bryophytes

Liverworts (Phylum Hepatophyta)

-*Thallus* ---> flattened lobed leafy structure -Asexual & sexual reproduction *Gemmae* ---> sm. tissue that grows on thallus (asexual reproduction) not differentiated into leaves, stems, or roots -Hairlike rhizoids on the underside of the thallus anchor plants to the soil -Lack stomata, although some have surface pores analogous to stomata -*The life cycle* is basically the *same* as that of mosses -Sexual reproduction involves production of gametangia on the haploid gametophyte -some gametangia are borne on stalked structures (archegoniophores and antheridiophores) -Some liverworts reproduce asexually by forming tiny balls of tissue called gemmae -Have flattened gametophytes with liverlike lobes -fixed open pores that cannot close, unlike stomata -80% look like mosses -single celled rhizoids aid in absorption -Form gametangia in umbrella-shaped structures

Mosses (Phylum Bryophyta)

-*only* living nonvascular plants -typically small -rhizoids ---> anchoring structures -many have separate sexes male = antheridia female = archegonia -protonema ---> filamentous cells produced by germinating spores leaf-like blades -play an important role in forming soil grow on rocks organic layer for other plants grow -Only plants with a *dominant gametophyte* generation - sporophytes remain permanently attached -Usually live in dense colonies or beds *Play an important role in forming soil; are important commercially (Sphagnum); and form peat bogs used for fuel* - found mostly in tropics, also found in Artic/Antarctic, not found in deserts

Hornworts (Phylum Anthocerophyta)

-100 spp. w/ narrow, pipe-like sporophyte -Found in disturbed habitats fallow fields Roadsides -stomata found on sporophyte -*indeterminate growth* (meristems continue to conduct cell division) grows throughout life of plant -symbiotic relationships w/ cyanobacteria -Superficially resemble liverworts, but cell structure resembles certain algal cells more than plant cells -Archegonia and antheridia are embedded in the gametophyte thallus rather than on archegoniophores and antheridiophores -single gametophyte often produces multiple sporophytes; meiosis occurs, forming spores within each sporangium -photosynthetic sporophyte

Whisk Ferns

-Found in tropics -Sporophyte consists of evenly forking green stems without true leaves or roots -Some gametophytes develop elements of vascular tissue -Only one known to do so -lacking veins and stomata -symbiosis with fungi

Plant Evolution

-Red algae, green algae, and land plants are collectively classified as archaeplastids -Molecular comparisons of DNA/RNA sequences suggest that land plants descended from a group of green algae (charophytes or stoneworts)

Fern Life Cycle

-Water is necessary for fertilization -Sperm are released on the underside of the gametophyte and swim in moist soil to neighboring gametophytes -Spores dispersed by wind. -pores are catapulted from the sporangium by snapping action -producing photosynthetic gametophytes that are often heart-shaped, are only one cell layer thick (except in the center), and have rhizoids that anchor them to their substrate -rhizoids are not true roots because they lack vascular tissue, but aid in transporting water/nutrients from the soil -Flask-shaped archegonia and globular antheridia are produced on either the same or a different gametophyte multicellular archegonia provide some protection for the embryo -sperm have flagella and swim

Some ferns & club mosses are heterosporous

-homospory -Heterosporous.

Club Mosses (Phylum Lycopodiophyta)

-small, evergreen plants with true roots; rhizomes and erect aerial stems -sporaphyte generation = dominate -scalelike leaves - microphylls (ONLY TO HAVE MICRO) -*strobili* ---> cone-like sporangium -common in temperate woodlands & tropics -coal formation -Lack seeds -small, unbranched veins -tropics and moist temperate regions -Superficially resemble true mosses -in some gametophyte is photosynthetic, some form symbiosis with soil fungi

Seedless Vascular Plants (Tracheophyte Plants; 420 MYA)

-specialized vascular tissues (phloem & xylem) -develops in sporophyte (not gametophyte) -true stems w/ vascular tissues most with true roots & leaves -leaves main organs of photosynthesis -microphylls (lycophyll) -megaphylls (euphyll) true leaves, found ONLY in seed plants/ferns (horsetails), angiosperms, gymnosperms -gametophyte & gametangia reduced 7 extant phyla grouped in three clades Lycophytes (club mosses) Pterophytes (ferns, whisk ferns, and horsetails) Seed plants

Fern sori

-sporangia** -Diploid spore mother cells in each sporangium undergo meiosis, producing haploid spores.

sporophyte

-spore-producing by meiosis in sporangia where diploid spore mother cells (sporocytes) undergo meiosis to produce 4 haploid spores -diploid (2n) phase in the life cycle of a plant having alternation of generations

Phylum Bryophyta (mosses) Phylum Hepatophyta (liverworts) Phylum Anthocerophyta (hornworts)

3 Phyla of Bryophytes

heterosporous

: production of 2 types of spores microspores ---> male gametophytes megaspores ---> female gametophytes -Forerunner of the evolution of seeds

moss protonema

A mass of green, branched, one-cell-thick filaments produced by germinating moss spores.

Horsetails

All 15 living species are homosporous -Constitute a single genus, Equisetum -Sporophyte consists of ribbed, jointed photosynthetic stems that arise from branching rhizomes with roots at nodes -Silica deposits in cells - scouring rush -one is green and photosynthetic, other brownish at termination in spore-producing cone

haplodiplontic

All land plants are _____

small, large

Angiosperms have _____, dependent gametophyte _____ sporophyte

green alga

Biologists hypothesize that all land plants evolved from a common ancestor, an ancient ___ ___ -Green algae and plants share many biochemical and metabolic traits -single species of freshwater photosynthetic algae gave rise to land plants

Fern fiddlehead

Center

stems

Did roots or stems evolve first?

Moss archegonia

Female- right may develop on same gametophyte as male gametangia or separate plants -single egg produced

Bryophytes (nonvascular plants) Seedless vascular plants Gymnosperms Angiosperms (flowering plants)

Four major groups of plants

Bryophyta = moss Hepatophyta = liverworts Anthocerophyta = hornworts seedless and non-vascular; gametophyte generation dominates

Give the name and common name of the 3 bryophyte phyla. What characteristics unite the groups?

Microphylls are small, with a single vascular strand; megaphylls typically larger and each possesses more than one vascular strand (weebing of vascular tissue)

How does one distinguish between megaphylls & microphylls?

female

Is the sporophyte male or female?

Moss antheridia

Male- left

large, dependent

Moss have _____ gametophyte Small, _____ sporophyte

Haplodiplontic Life Cycle

Multicellular diploid stage - sporophyte Produces haploid spores by meiosis Diploid spore mother cells (sporocytes) undergo meiosis in sporangia Produce 4 haploid spores First cells of gametophyte generation Multicellular haploid stage - gametophyte Spores divide by mitosis Produces gametes by mitosis Gametes fuse to form diploid zygote First cell of next sporophyte generation *both stages are MULTICELLULAR *gametes produced by MITOSIS -humans are diplonti- only diploid stage is multicellular

deserts

Plant habitats range from arctic tundra to tropical rain forests to harsh ____

multicellular embryos

Unlike green algae, all land plants develop from ___ ____enclosed in maternal tissues

Fern have vascular tissues with true roots and leaves.

What adaptations do ferns have that both algae and bryophytes lack?

about 445 MYA

When did land plants evolve from green algae?

Chlorophytes Charophytes

green algea two major clads

Issues and adaptation of landplants

land is dry, plants have to avoid drying out -----> *waxy cuticle* prevents plant tissues from drying out; vascular system organic molecules & CO2 has to diffuse into the chloroplast with little water loss ----> stomata allow gas exchange through the cuticle as result of waxy cuticle limiting gas exchange embryo needs to be protected during development ----> female *gametangium* protects the developing embryo & diffuses org. mol w/o losing water diploid bodies mask recessive deleterious mutations caused by UV radiation

Antheridia

male gametangia that form sperm cells

gametangia

multicellular organs that produce gametes

xylem

tissue that carries water is called

gametes

what does the gametophyte produce?

spores

what does the sporophyte produce?

410 MYA

when did vascular plants first appear?