Seedless and Seedless Vascular Plants

Most common ancestor of plants

Archaeplastida→Charophytes

Green Algae and Plants: Shared Characteristics

Chlorophytes, Charaphytes and Plants share:

• multicellularity

• cell walls with cellulose

• chloroplasts with the same pigments (a+b)

• Storage molecule is starch

Chlorophyte (Ulva), Charophyte (Chara), plant (moss)

Challenges from water to Land

Desiccation (drying out is a constant danger for an organism exposed to air)

Both gametes and zygotes must be protected from dessication

Plants needs to form structural support in a medium that does not give the same lift as water

Male gametes must reach the female gametes using new strategies, swimming is no longer possible

Benefits from water to Land

[CO2] is higher

light intensity is higher

more minerals

no herbivores

no competition

From land to water: Adaptations

Life cycle: alternation of generations

Apical meristem tissue in roots and shoots

Waxy cuticle to resist dessication

Cell walls with lignin to support structures off ground

Alternation of generations: bryophytes

archegonium

where fertilization occurs

protects egg

the female part of the plant

gametangia (multicellular gamete)

where zygote formation occurs

Apical Meristems

continuously dividing cells

roots and shoots grow towards resources

Waxy Cuticle

stop desiccation

pores needed in this to allow CO2/O2 exchanges

Sporopollenin

Protects haploid spores when there’s dispersal through air

made with multicellular sporangium

Antheridium

gametangia

protect sperm

male part of the plant

Why Charophyte life cycle if different from plants

The zygote is unicellular and not multicellular when going from meiosis to fertilization

Stomata

Holes for gas exchange in plant leaves below cuticle

Secondary metabolites

Chemicals adapted in plants to deter, repel or poison competitors, herbivores, and parasites

Mycorrhizae

Mutualism w/ fungi; helps plants get water and absorb minerals

dates back to the first land plants (before true roots)

Seedless Nonvascular Plants (SNP)

Bryophytes

Non-woody, small, ground-covering plants that require water for reproduction

Have rhizoids (Not true roots)

Phyla of Bryophytes

Liverworts (Hepaticophyta group)

Hornworts (Anthocerotophyta group)

Mosses (Bryophyta group)

Seedless Nonvascular Plants

Homosporous

Bryophyte characteristics: Gametophyte

Haploid gametophyte dominant

makes eggs and flagellated sperm

most are small, low growing, in moist areas

Bryophyte characteristics: sporophyte

Sporophyte depends on gametophytes for food and water

Grows w/in archegonium of gametophyte

sporangium makes many haploid sperms

Liverworts

Most have elevated gametophytes that resemble miniature trees (Marchantia)

Reduced over very small sporophytes; some thalloid some leafy

Marchantia, thalloid=gametophyte

Plagiochilla deltoids, leafy= gametophyte

Bryophytes

Bryophytes, hepaticophyta

Hornworts

common name refers to the horn-like long tapered shape of sporophyte

good colonizers of moist soils

symbiotic relationship with nitrogen-fixing cyanobacteria

Bryophytes, Anthocerotophyta

Mosses

The most numerous of the non-vascular plants

inhabit extreme environments such as mountain tops, tundra, and deserts

Sporophyte grows up from female gametophytes to gain elevation for spore dispersal (polytrichum commune, hair-cap moss)

Pioneer species in nutrient-poor soils

primary producers in cold/high-altitudes

Sphagnum/Peat Moss; important in wetlands, also harvested for food

Some peatlands preserve corpses for thousands of year

Bryophytes, Bryophyta

Seedless Vascular Plants Characteristics (SVP)

Branched sporophytes that are independent of gametophytes for nutrition

diploid sporophyte dominates life cycle

Transport in the xylem and phloem (vascular system)

Evolution of true roots

Evolution of true leaves

Microphyll Leaves

small, spine-shaped leaves

supported by a single strand of tissue

SVPs

Ex: Krauss’ spike moss, selaginella kraussiana

Megaphyll

leaves supported by a branched vascular system

Greater photosynthetic productivity

Ex: Tumbridge filmy fern, hymeniphylllum tumbrigense

SVPs

Sphorophylls

Leaves modified to bear sporangia

Developed in SVPs

Ex: Sori on ferns

Sphorophylls: Homosporous

Sporangium on sporophyll → single type of spore → typically bisexual gametophyte → Eggs/Sperm

Sphorophylls: Heterosporous

Megasporagnium on megasporophyll →Megaspore → Female gametophyte → Eggs

Microsporangium on microsporophyll → Microspore → Male gametophyte → Sperm

SVPs

Lycophytes (club mosses and relatives)

Pterophytes (ferns and relatives)

Lycophytes

small, tropical, and temperate

Sporophylls are modified to be cone-like strobilus

Only phyla to have microphyll leaves

Seedless Vascular Plants

Mainly monoecious

Sporophyll: cone-like structure/ central stalk

Lycophytes: Homosporous

Club mosses

Lycophytes: Heterosporous

quillworts and spike mosses

Pteridophytes

Horsetails, whisk ferns, and ferns

Homosporous → monoescious

Heterosporous → diescious

Sorophyll: Sori

Whisk Ferns

dichotomous branching

no true leaves or roots

homosporous

photosynthesis occurs in the stem

Pteridophytes, SVP

Monilphyte

Psilotum

Horsetails

Joined stems with tiny leaves

Strobili

Homosporous

Photosynthesis occurs in stems

Pteridpohytes, SVPs

Monilophytes

Ferns

most widespread and diverse

Homosporous

large megaphylls

sori on the underside of sporophylls

mostly in understory or as epiphytes

SVPs

Pteridophytes

Monilophyte group

Fern Life Cycle

Importance of Seedless Plants (SVPs and Bryophytes)

The disappearance of mosses→Biological indicator of environmental pollution

Ferns→ Promotes Weathering of rocks → accelerates topsoil formation

Ferns→ Used as food

Peat Moss → used as fuel (renewable resources)

Peat Moss → Soil conditioner

Extinct SVPs → Coal → Energy source