Chapters 29 & 30
Protists Land Plants.
Plantae. Draws line @ embryophytes.
GREEN ALGAE [29.1]
Closest relationship charophyceans (esp these 2 genera: chara and
Plants are multicell photosynth autotroph eukaryo like red, brown and
some green algae. Cell walls and chlorophyll a and b overlap
Plant & Charophyceans alike:
1. Rosette cellulose-synthesizing complex (prot synth cellulose
microfibrils for cell wall cf linear arrangement in noncharophycean
2. Peroxisome enzymes present in Charophyceans peroxisome that
minimise organic product loss due to photorespiration.
3. Flagellated sperm. In land plants w flagellated sperm, structure v
similar w charophycean sperm.
4. Phragmoplast formation (phragmoplast = cytoskeleton alignment &
coalising of golgi-derived vescicles that form cell plate during
Many charophycean species live shallow waters where exposed to drying
out. Contain sporopollenin = layer durable polymer prevent drying out
precursor to tough sporopollenin walls encasing plant spores
Terrestrial adaptations [29.2]
Plant differences w charophyceans:
1. apical meristem, sustain growth by localised regios of cell div @ shoot
and root tips. Cells diff to various tissues.
2. alternation of generations. Gametophyte (haploid), mitosis (produce
gametes), fertilization, zygote, mitosis, sporophyte (spore-producing
generation), meiosis, mitosis, gametophyte.
3. sporangia producing walled spores from sporocytes (undergo meiosis).
Sporopollenin – chemical adaption.
4. multicell, dependent embryo – has specialised placental transfer cells,
sometimes in adj maternal tissue, increase nutrient transfer via
elaborate ingrowths of wall surface (PM & cell wall)... why called
5. multicell gametangia, where gametes produced. Female archegonia, -
vase shaped organ w single egg retain w/in base of organ. Male
antheridia –prod/release sperm into environm.
Dvp of cuticle (polymers of polyesters + waxes)
Produce secondary compounds – secondary mtabolic pthways (side
braches of primary mtabolic pthways –those produce lipids, carbohydrates,
amino acids– common to all organisms). Aids survival
Vascular tissue vascular plants.
Nonvascular plants bryophytes (liverworts, hornworts, mosses)
w/out real roots and leaf system.
Seedless vascular plants lycophytes (club moss, quill worts, spike
mosses) & pterophytes (ferns, horsetails). Clade not monophyletic.
Vascular seed plants gymnosperms (naked seeds – seed not
enclosed in chambers & angiosperms (all flowering plants – seed dvp
Gymnosperms: Cycadophyta, ginkgophyta, gnetophyta,
Angiosperms: All anthophyta. Monocots form a clade but remaining
angiosperms possibly not monophyletic. Most dicots = eudicots “true
dicots”. Others divided into lineages: 3 together form Basal
angiosperms, another lineage: magnoliids.
Terminology: Bryophyta – exclusively mosses. Bryophytes – include
all nonvasc plants.
Gametophyte dominant = larger, longer living than sporophytes.
Germinating moss produce mass of green, branched, 1-cell-thick
filmts protonema increase SA for absorb of water + minerals.
Produce buds w apical meristem gen gametophore, gamete-produc
structure. Gametophore + protonema = body of moss gametophyte.
Rhizoids anchor gametophyte. Long tubular cells in worts, filaments
in mosses. Not roots, cuz no vasc tissue.
Mature gametophytes prod gametes in gametangia covered by
protctive tissue. Most bryophytes have sep male/fem gametophytes
w antheridia/archegonia produce sperm/egg. Flagellated sperm swim
to egg at archegonia base in response to chemical attractants
through film of water.
Post-fertilization: embryo remain in archegonia, layers of placental
transfer cells transport nutrients to embryo while embryo dvp into
Bryophyte Sporophytes [29.3]
Bryophyte sporophyte (smallest + simplest of all plant groups) are
photosynthetic when young but not independent. Remain attached
to gametophyte parent, absorb nutrients.
Fertilization zygote sporophyte by mitosis, attached by foot to
gametophyte grows long stalky seta that emerges from
Nutrients conducted from foot to seta to sporangium aka capsule
produce spore by meiosis. Immature capsule protected by
gametophytic tissue calyptra (shed when capsule mature).
Upper capsule feature ring of toothlike structures peristome
specialised for gradual spore discharge. Advtg of periodic wind gusts
carry spores long distances.
Hornworts + moss have stomata, liverworts don’t. Mosses can
suffer severe dessication. Forms extensive deposits (peat bogs) of
partially decayed organic materal (peat). Inhibit decay.
Seedless Vascular Plants
Lycophytes (qillworts, spike mosses, club mosses), & Pterophytes
(Ferns, horsetail – sometimes arthrophytes due to jointed stems).
Sperm are flagellates, swim through water film to reach eggs.
Fragile gametophytes. Need damp environments.
Dominant (length wise same, complexity wise sporophyte greater)
sporophyte not gametophyte-dependent. Branching = more complex
body increase efficiency w many sporangia, increase survival.
Vascular system = xylem (tracheids lignified, no vessel elemnts – vasc
plants sometimes tracheophytes)/phloem (sieve-tube membrs), roots
and leaves (microphylls, spine shaped w single vein cf megaphylls,
highly branched vasc system), spore-bearing leaves sporophylls on
underside have sori (sorus) – clusters of sporangia. Strobili – cones
formed by groups of sporophylls
Homosporous – one type of sporophyll produce one type spore
that dvp into bisexual gametophyte cf Heterosporous has 2 types of
sporophylls give 2 diff spores. Megasporangia megaspores
female gametophytes. Microsporangia in microsporophyll
microspores dvp male gametophytes.
Seedless Vasc Life Cycle
Spore Young photosynthetic gametophyte (usually bisexual,
though can be from megaspore or microspore)
Mechanisms promote cross-fertilization. Bisexual gametophytes
have antheridium/archegonium structures that prod sperm and egg.
Flagellated sperm swim from antheridia to archegonia
Fertilization dvp into sporophyte
Sporophyte grows from out of archegonium of parent gametophyte.
Mature sporophyte have sporophylls with sori on underside.
Meiosis occurs in sporangia. Sporangia release spores.
Gametophyte shrivels and dies after young sporophyte detaches
Seed Plants [30.1]
Emergence/diversification of seed plants.
1. Reduced gametophytes – microscopic in seed plants. Gametophyte
dependent on sporophyte for nutrients. Miniaturization allowed
spores to be retained w/in sporangia of parental sporophyte
protect gametophores from ext stress.
2. Heterospory (all seed plants, & in some seedless plants)
Megasporangia/microsporangia produce mega/microspores giving
to fem/male gametophytes. Megasporangium one single function
megaspore. Microsporangium many function microspores.
3. Ovules (megasporangium, megaspore, integuments) – one (in
gymnosperms) or two (in angiosperms) integuments from
sporophytic layers envelop/protect megasporangium. In each ovule,
female gametophyte dvp from megaspore, produce 1+ egg cells.
4. Pollen grains dvp from microspores, protected by tough
sporopollenin coat. Transfer by pollination. Pollen grain germination
pollen tube discharge 2 sperm into ovule through micropyle
ovule dvp into seed (embryo + food suply w/in seed coat from
integuments) – resists harsh environment, disperse widely
Progynosperms (heterosporous plants acquiring adaptations
characterising seed plants but don’t produce seeds)
Naked seeds not enclosed in ovaries but exposed on modified
leaves that form cones (strobili) – cone bearers are conifers.
Ovulate cone has scales, each has two ovules, each containing a
Pollen cone contains many microsporangia (each contain many
microsporocytes that will dvp into microspores after meiosis into
haploids pollen grains) held in sporophylls.
Pollen grain enters through micropyl, germinates, form pollen tube
slowly digesting through megasporangium, meanwhile
megasporocyte meiosis prod 4 haploid, one megaspore survive.
W/in megaspore, female gametophyte dvp, contain few archegonia
each w egg.
Sperm cells would’ve dvp in pollen tube which extends to female
gametophyte. Fertilization of nuclei. only one zygote dvp into
Flowering plants – flowers = reproductive organs spec for sexual
reproduction. Require pollination. Receptacle, sepals, petals, stamens
(filament + anther) are microsporophylls (NB: flower organs are mod
leaves), carpels (stigma, style, ovary) = megasporophylls which make
megaspores & fem gametophyte. Single/fused carpels sometimes called
Fruit (fleshy or dry) from mature ovary (can incl other flower parts).
Seeds dvp from ovules, ovary wall thickens pericarp.
LIFE CYCLE: flower of sporophyte has micro/megasporangia that
produce microspores (prod male gametophytes) in pollen grains and
megaspores (prod female gametophytes). Pollen grain to stigma.
Self/cross-pollination. Pollen grain 2 haploid: tube cell that forms
pollen tube and generative cell that divides in tube cell. Tube cell
penetrate ovary via micropyle (pore in integuments), discharge 2 sperm
cells into embryo sac. One generative cell fertilizes egg diploid zygote.
Other fuse w 2 nuclei of large central cell of female gametophyte
(embryo sac) = double fertilization. zygote dvp into embryo
(rudimentary root + cotelydons), packaged w food (endosperm dvp from
triple nuclei nucleus of central fem gametophyte cell in seed.
Evo-devo hypothesis: ancestor angiosperm sep micro/megasporophylls.
Angiosperms Diversity [30.3]
Monocots have one cotyledon in embryo, parallel leaf veins,
vascular tissue scattered, root system often fibrous, pollen grain w
one opening, floral organs in multiples of three.
Dicots have two embryonic cotyledons, netlike leaf veins, ring-
arranged vascular tissue, taproot system usually, three opening on
pollen grains and floral organs multiples of four or five.
Coevolution between angiosperms and animals shown often