����Land Plants, Part 1: �The Bryophytes�Mosses, Liverworts, and Hornworts

Spring 2020

Eukaryote Cladogram

Eukaryotes have a nucleus, and other membrane-bound organelles

Archaea

Bacteria

Nucleus

Major groups of Eukaryotes

• Red algae, Green algae, Land plants
• Brown algae, Diatoms, Water molds
• Fungi, Slime molds, Animals

Prokaryotes

Plant Clade

• Clade includes the Red algae,

Green algae, and Land plants

• Chloroplasts came from endosymbiosis with cyanobacteria
• This clade is called Archaeplastida meaning “first chloroplast”
• Eukaryotes perform sexual reproduction

Red algae

Chloroplasts from cyanobacterium

Archaea

Red algae

Green algae

Land plants

Plants

Eukaryote�Sexual Lifecycles

Diplontic Lifecycle

Haplo-diplontic Lifecycle

Haplontic Lifecycle

Lifecycle Terminology

• Diploid phase: two sets of chromosomes (2n) in each cell

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• Haploid phase: one set of chromosomes (1n) in each cell

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• Meiosis: process by which a diploid “mother cell” is reduced to 4 haploid cells; 2n⇨1n+1n+1n+1n
• Fertilization: process by which haploid cells fuse to create a diploid cell (embryo); 1n+1n ⇨ 2n

Types of Lifecycles

• Diplontic lifecycle
• Diploid phase is multicellular
• Haploid phase is not multicellular
• Gametes created through meiosis
• e.g., Animals, like us!
• Diplo-haplontic lifecycle
• Diploid and haploid both multicellular
• Spores created through meiosis
• e.g., All plants
• Haplontic lifecycle (session 6)
• Haploid phase is multicellular
• Diploid phase is not multicellular
• Zygote immediately goes through meiosis after fertilization
• e.g., Fungi

Haploid (1n)

M

=Meiosis

F

=Fertilization

Diploid (2n)

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Mature

Diploid

Organism

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matures

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+

+

Diplontic Lifecycle

Diploid phase

is dominant

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Found in animals and some algae

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-

+

-

Gametes

zygote

Haploid

Diploid

♂

♂

Fertilization

Meiosis

Gametes from another organism

Mature

Haploid

Organism

Gametophyte

(1n)

Mature

Haploid

Organism

Gametophyte

(1n)

Mature

Diploid

Phase

Sporophyte

(2n)

Diplo-haplontic

Lifecycle

Spores (1n)

Male gametes

Female gametes

Found in all land plants

Sporangium

(2n)

♂

♀

Gametes (1n)

Zygote

(2n)

Spores from another organism

♀

♂

♂

♂

Fertilization

Meiosis

Either phase could

be dominant

Diplo-Haplontic Lifecycle

Sporophyte (2n): multicellular, diploid phase

• Spore-producing phase of a plant
• Zygote/embryo (2n): a young sporophyte formed from fertilization
• Sporangium (2n): a spore sac; a container that creates and holds spores (plural = sporangia)
• Spores (1n): haploid cells formed through meiosis, which germinate into gametophytes

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Gametophyte (1n): multicellular, haploid phase

• Gamete-producing phase of a plant
• Gametangium (1n): a sperm-producing or egg-producing structure (plural = gametangia)
• Gametes (1n): haploid reproductive cells, such as a sperm or egg, that fuse to form sporophytes

“-phyte” = plant

“-angium” = vessel

Diploid

Phase

(multicellular)

F

Haploid

Phase

(multicellular)

Gametes

Spor-angium

M

Zygote

Spores

Gamet-angium

MEIOSIS

Mature

gametophyte

(1n)

Diplo-Haplontic

Lifecycle

Both phases multicellular;

Either phase can be dominant

Embryo (2n)

is retained

Spores (1n)

Mature

gametophyte

(1n)

Mature

Sporophyte

(2n)

Spore

Dispersal

Germination

FERTILIZATION

Land Plant Lifecycle

• Land plants have a Diplo-Haplontic (or Haplo-Diplontic) lifecycle
• Female gametophyte creates a gametangium with an egg
• Sperm swim to the egg, fertilize it, creating a diploid cell…
• …which is retained in the female, thus it is called an embryo
• The embryo grows, and is nourished by the female gametophyte
• Embryos define the land plants (therefore, they are called embryophytes)

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leaf

leaf

Female gametophyte (1n)

Land plants = Embryophytes

Embryo: result of fertilization; retained on and nourished by female gametophyte (e.g., plants)

Zygote: result of fertilization; not retained on female gametophyte (e.g., algae)

Sperm (1n)

FERTILIZATION

Land Plants or Embryophytes

Defining feature: embryos

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• Bryophytes
• Spore-bearing, non-vascular plants
• Pteridophytes
• Spore-bearing, vascular plants
• Gymnosperms
• Cone-bearing, seed plants
• Angiosperms
• Flowering/fruiting plants

Vascular Plants

Embryos

Liverworts

Embryophytes or Land Plants

Green algae

Hornworts

Mosses

Lycophytes

Ferns & allies

Cycads

Angiosperms

Conifers, Ginkgo

Land Plants (Embryophytes)

Embryophyte Terminology

Sporophyte: multicellular diploid phase

• Spore-producing phase of a plant
• Embryo: a young sporophyte formed from fertilization, protected/nourished by the female gametophyte
• Sporangium: spore case; container that creates spores
• Spores: cells formed through meiosis that produce gametophytes

Gametophyte: multicellular haploid phase

• Gamete-producing phase of a plant
• Gametes: reproductive cells, such as a sperm or egg, that fuse to form sporophytes
• Antheridium: a male gametangium; produces sperm
• Archegonium: a female gametangium; produces an egg

Bryophytes

• Earliest land plants on Earth
• Found on every continent; diverse in the tropics
• There are 3 groups of bryophytes
• Mosses, Liverworts, and Hornworts
• Non-vascular plants: no xylem; no phloem
• Spore-bearing plants (no seeds)
• Most have root-like organs (=rhizoids)
• Haplo-Diplontic life cycle
• Sporophyte
• Epiphytic, not photosynthetic
• Gametophyte
• Dominant, photosynthetic
• Both are multicellular

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Liverworts

Hornworts

Mosses

Bryophytes

Mosses

• Most diverse bryophytes (~12,000 spp.)
• Stems have spiraling leaves
• Root-like rhizoids: anchor plant, minimal absorption of water/minerals
• Gametangia in clusters at tip of gametophyte (“splash cups”)
• Female gametangia called archegonia
• Male gametangia called antheridia
• Sporophyte ends in a sporangium (capsule)
• No leaves on sporophyte

Leaf x.s.

Stem x.s.

Stem l.s.

Moss

Gametophytes

Moss Lifecycle

Sperm (1n)

Egg (1n)

Male gametophyte

Male gametophyte

Female gametophyte

Female

gametophyte

Male

gametophyte

Archegonium (1n)

Antheridium (1n)

Film of water

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Springtails

Foot

Stalk

Capsule