Lecture 4 Bryophytes

Bryophytes

Non-vascular land plants

Bryophyte life cycle

*conspicuous gametophyte and sporophyte

Name the bryophyte lineages

Hornworts, liverworts, and mosses

Why are bryophyte lineages controversial?

Some think bryophytes are a clade, while others do not.

A monophyletic bryophyte is…

increasingly supported.

Describe bryophyte characteristics

-No true roots, stems, or leaves → homoplasy

-Move water via osmosis

-No strong support tissue

-Signaling proteins for dessication tolerance

-Most abundant in moist habitats but are very resilient

-Mostly small (no vascular system)

-Minerals can be distributed throughout body via diffusion

Hornworts

-~100 extant species

-Look like small horns

-Contain one chloroplast

-Sporophyte grows from basal meristem

-Permanently open stomata on sporophyte

-Symbiotic relationship with cyanobacteria that live within internal cavities

-Many symbiotic relationships

Mosses

-~15,000 extant species

-Have hydroids (die and leave channel through which water can move)

-Sporophyte attached and dependent on gametophyte

-Sporophyte unbranched

-Many have stomata on capsules

-Peristome teeth aid dispersal

Peristome teeth

-Hygroscopic

-Allow gradual dispersal of spores

What is an ecologically significant moss? Why?

Peat moss → carbon sinks that regulate the global climate; low-oxygen conditions prevent things from fully decomposing

Liverworts

-Green, flat leaf-like gametophytes

-Growth occurs at apex of plant

-Sporophyte remains attached to larger gametophyte

-Reproduce asexually and sexually

-No internal water conduction

-No true stomata

-Gemmae for asexual reproduction

Morphology supports the hypothesis that:

Mosses + liverworts form a natural group.

Liverwort sporophytes

-Stalk (seta) + capsule (the sporangium)

-Sporophyte attached to gametophyte and dependent on it

-Seta elongates by cell elongation throughout its length

-Sporangia split along sutures

Hygroscopic elaters

Assist in spore dispersal by flexing in response to humidity

Sporangia

Structures that produce and contain spores

Liverwort adaptations

-Rhizoids: Anchor plant, water absorption

-Large surface area for absorption

-Gemma cups allow asexual reproduction

Mosses adaptations

-Rhizoids

-Sporophyte = foot, seta, capsule

-Peristome teeth

→ Mosses can reproduce and disperse without sporophyte living independently

Hornworts adaptations

-Foot embedded in gametophyte

-House nitrogen-fixing cyanobacteria

-Rhizoids

Bryophytes are ___ dominant.

gametophyte

Bryophytes are ____ for fertilization.

water-dependent

How did Penny Chisolm’s lab identify Perchlorococcus?

Fluorescence of chlorophyll in seawater

Which traits identify mosses from other plants?

Land plants lacking vascular tissue