Green Plants
description
Transcript of Green Plants
Green Plants
Biol 366Spring 2011
Tree of Life: The Big Picture
EukaryotesArchaeaBacteria
ca. 4 bya
now
>3.5 bya
>2 bya
membrane-boundnucleus, 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
Basal streptophytes: Fig. 7.4 from the text
Chlorophytes: Fig. 7.3 from the text
Conjugation inSpirogyra
Haplontic life cycle (haploid dominantor zygotic meiosis)
The only diploid cellthe zygote
CharalesHaplontic but some havemulticellular gametangia(gamete-producing structures)
Embryophytes (land plants) share:
• Cuticle• Alternation of generations (multicellular
sporophyte and multicellular gametophyte)
• Multicellular gametangia (gamete-producing structures)
• Multicellular sporangium (spore-producing 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
LiverwortMulticellular gametangia(male = antheridia)
LiverwortMulticellular gametangia (female = archegonia)OogamyRetention of zygote within the female gametophyteMulticellular 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, whisk-
ferns, 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
Selaginella
Lycopodium and friends
Isoetes (quillwort)
Whisk-fern (Psilotum)
Ferns (Leptosporangia)
Monilophytes (ferns, horsetails, whisk ferns)
horsetails
1n spores
Gametophyte (1n)
Sporophyte (2n)
Nutritionally independentsporophytes andgametophytes
Fern Life Cycle
Fig. 8.4 from the text
Spermatophytes(seed plants)
• Secondary xylem (wood), heterospory, seeds
• Includes gymnosperms and angiosperms
Fig. 7.12 from the text
Gymnosperms• 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 scalebearing usually two ovules; directly exposed to pollen
Male cones with eachscale bearing two or more microsporangia
Section of female pine cone
pine pollen
pine microsporangia
Pine seeds
Pine seedling—next sporophyte generation
Angiosperms• “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 highlymodified 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