Transcript Plant Anatomy: Intro to Plant Reproduction

Green Plants
Biol 366
Spring 2011
Tree of Life: The Big Picture
now Bacteria
Archaea
Eukaryotes
>2 bya
>3.5 bya
ca. 4 bya
membrane-bound
nucleus, organelles,
etc.
Fig. 7.1 from the text
Green plants share:
• Chlorophylls a and b
• Starch storage
• Stellate flagellar structure
• Certain gene transfers from the
chloroplast to the nucleus
Green plant diversity:
• > 300,000 species
• Two major groups: 1) chlorophytes
(marine and other green algae) and 2)
streptophytes [freshwater green algae
and embryophytes (= land plants)]
• A major branch (clade) in the
eukaryotic Tree of Life
Fig. 7.2 from the text
Chlorophytes: Fig. 7.3 from the text
Basal streptophytes: Fig. 7.4 from the text
Conjugation in
Spirogyra
Haplontic life cycle
(haploid dominant
or zygotic meiosis)
The only diploid cell
the zygote
Charales
Haplontic but some have
multicellular gametangia
(gamete-producing structures)
Embryophytes (land plants)
share:
• Cuticle
• Alternation of generations (multicellular
sporophyte and multicellular
gametophyte)
• Multicellular gametangia (gameteproducing structures)
• Multicellular sporangium (sporeproducing structure)
• Embryo (young sporophyte)
Bryophytes
• Hornworts, liverworts, mosses
• Gametophyte-dominant
• No vascular tissue (except conducting
cells in a few mosses)
• Separate male and female
gametophytes
• Sperm must swim to the egg, therefore
need water for fertilization and
therefore must remain small
Fig. 7.5 from the text: liverworts, mosses and hornworts
Fig. 7.6 from the text
Hornwort sporophytes and gametophytes
Liverwort thallus (gametophyte) showing air pores
Liverwort
Multicellular gametangia
(male = antheridia)
Liverwort
Multicellular gametangia
(female = archegonia)
Oogamy
Retention of zygote within the
female gametophyte
Multicellular embryo
Moss male gametophyte
(= antheridia)
Capsule = sporangium
of the sporophyte
Tracheophytes (vascular plants)
• Vascular tissue (tracheids) present
• Include lycophytes, monilophytes
(ferns, horsetails, whisk ferns), and
spermatophytes (seed plants)
Fig. 7.8 from the text
Monilophytes and Lycophytes
• Ferns, horsetails, quillworts, whiskferns, etc.
• Independent gametophytes and
sporophytes
• Sperm must still swim to the egg
• Most are homosporous; a few evolved
heterospory
• Many homosporous ferns have means
of avoiding self-fertilization
Lycophytes
Isoetes (quillwort)
Lycopodium
and friends
Selaginella
Monilophytes
(ferns, horsetails, whisk ferns)
horsetails
Whisk-fern (Psilotum)
Ferns (Leptosporangia)
Nutritionally independent
sporophytes and
gametophytes
Sporophyte (2n)
Gametophyte (1n)
1n spores
Fig. 8.4 from the text
Fern Life Cycle
Spermatophytes
(seed plants)
• Secondary xylem (wood), heterospory,
seeds
• Includes gymnosperms and
angiosperms
Fig. 7.12 from the text
Gymnosperms
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•
Conifers, gingko, cycads, Gnetales
Heterosporous (male and female sporangia)
Sporophyte-dominant
Antheridia lost, replaced by pollen (= male
gametophyte)
• Archegonia present but reduced, embedded
in nutritive tissue of the megasporangium (+
integument = ovule)
• Bear seeds (= fertilized, embryo-containing,
unopening ovule)
Female cone with each scale
bearing usually two ovules;
directly exposed to pollen
Male cones with each
scale bearing two or
more microsporangia
pine pollen
Section of female pine cone
pine microsporangia
Pine seeds
Pine seedling—next
sporophyte generation
Angiosperms
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“Dicotyledons”, monocotyledons
Heterosporous
Sporophyte-dominant
Pollen = male gametophyte
Archegonia lost; embryo sac = female
gametophyte; ovules enclosed in
carpels (indirect pollination)
• Double fertilization produces zygote +
primary endosperm nucleus
Flower = a short, determinate shoot bearing highly
modified leaves, some of which are fertile (i.e.,
bearing either microsporangia or megasporangia),
with the megasporangia in carpels
Fig. 4.17 from the text: Angiosperm life cycle
Animal pollination syndromes
Wind pollination