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Introduction to Plants
Figure 29.1
Charophytes
Figure 29.2
ANCESTRALALGA
Red algae
Chlorophytes
Charophytes
Embryophytes
Virid
iplan
taeStrep
top
hyta
Plan
tae
Relationship between algae and land plants
Green Algae & Plants: shared traits
• Chlorophyll A & B• Cell walls of cellulos• Starch as polysaccharide for storage
30 nm
Charophytes as closest relatives
Shared traits w/ land plants• Protien rings on cell membrane to make cellulose• Similar sperm (assymetrical arranged flagella)• Phragmoplasts (microtubule arrangement during mitosis)• Nuclear and chloroplast DNA similarities• Some charophytes protect zygote w/ in gametophyte
Derived Traits of Plants• Five key traits appear in nearly all land plants
but are absent in the charophytes– Alternation of (heteromophic) generations – Multicellular, dependent embryos– Walled spores produced in sporangia– Multicellular gametangia– Apical meristems – Cuticle– Stomata (except liverworts)
Figure 29.3a
Alternation of generations
Gametophyte(n)
Gamete fromanother plant
Mitosis
GameteSpore
Mitosis
Mitosis
Zygote
Sporophyte(2n)
Key
Haploid (n)
Diploid (2n)
n
n
n
n
2n
MEIOSIS FERTILIZATION
Figure 29.3b
Multicellular, dependent embryos
Embryo (LM) and placental transfer cell (TEM)of Marchantia (a liverwort)
Embryo
Maternaltissue
Wallingrowths
Placentaltransfer cell
(blue outline)
10 µm2 µm
Figure 29.3c
Walled spores produced in sporangia
Sporophytes and sporangia of Sphagnum (a moss)
Spores
Sporangium
Longitudinal section of Sphagnum sporangium (LM)
Sporophyte
Gametophyte
Figure 29.3d
Multicellular gametangia
Femalegametophyte
Archegonia,each with anegg (yellow)
Antheridia(brown),containing sperm
Malegametophyte
Archegonia and antheridia of Marchantia (a liverwort)
Figure 29.3e
Apical meristems
Apical meristemof root
Apical meristemof shoot
Developingleaves
Root Shoot
Apical meristems of plant roots and shoots100 µm 100 µm
Figure 29.5
ANCESTRALGREENALGA Origin of land plants
Origin of vascular plants
Origin of extantseed plants
Liverworts
Mosses
Hornworts
Lycophytes (club mosses,spike mosses, quillworts)
Monilophytes (ferns,horsetails, whisk ferns)
Gymnosperms
Angiosperms
Lan
d p
lants
Vascu
lar plan
ts
No
nvascu
larp
lants
(bryo
ph
ytes)
Seed
lessvascu
larp
lants
Seed
plan
ts
500 450 400 350 300 50 0Millions of years ago (mya)
1
2
3
Plant Diversity:- non-vascular- seedless vascular- seed (but no flowers)- flowering plants (seed + flowers)
Table 29.1
Challenges of dry land
• Dryness/relative lack of water• Gravity (need for support)
Nonvascular plants (24,000 species)
Liverworts, hornworts, & mosses
Nonvascular plants1. Gameptophyte dominant2. Dependent sporophyte3. Flagellated sperm
– Consequences on reproduction?
4. Environment found?5. Non vascular tissue
– Size?– Environment found?
Figure 29.6
Key
Haploid (n)Diploid (2n)
Protonemata(n)
“Bud”
Sperm
Malegametophyte (n)
Antheridia
GametophoreSporedispersal
Spores
Peristome
Egg
Archegonia
Rhizoid
Sporangium
SetaCapsule(sporangium)
FootMature
sporophytes
MEIOSIS
Embryo
Zygote(2n)
FERTILIZATION(within archegonium)
Archegonium
Youngsporophyte(2n)
Capsule withperistome (LM)
2 m
m
“Bud”
Femalegametophyte (n)
Femalegametophyte
Animation: Moss Life Cycle
Figure 29.6a
Capsule with peristome (LM)
2 m
m
Figure 29.9
(a) Peat being harvested from a peatland (b) “Tollund Man,” a bog mummy datingfrom 405–100 B.C.E.
Seedless Vascular Plants• Ferns, club mosses, horsetails, wiskferns, etc..
Monilophytes (Phylum Monilophyta)
Strobilus onfertile stem
Vegetativestem
Athyrium filix-femina,lady fern
Equisetum telmateia,giant horsetail
Psilotum nudum,a whisk fern
4 cm
3 cm
25 c
m
Figure 29.13a
Seedless Vascular Plants: Lycophytes (Phylum Lycophyta)
Isoetesgunnii,a quillwortSelaginella
moellendorffii,a spike moss
Diphasiastrum tristachyum,a club moss
Strobili(clusters ofsporophylls)
2.5 cm
1 cm
Seedless Vascular Plants
• Sprophyte dominant– Independent gametophyte
• Flagellated sperm– Impact on reproduction
• Vascular Tissue– Transport– Support
Promotes increase in size
Vascular Tissue
• Xylem– Transports water and minerals (nutrients from
soil)– Provides support
• Phloem– Transports sugars
True roots, stems, & leavesRoots:• Length via apical meristem• Contain vascular tissues• Anchor and absorb
Leaves• Specialized for photosynthesis• Microphylls—single vein (of vascular tissue)• Megaphylls—multiple veins (of vascular tissue)• Sporophylls—leaves that create/house sporangia
Figure 29.14
Horsetail Fern
Seed plants: gymnosperms + angiosperms
Seed plant developments• Pollen
– Distribution (w/o water) and protection of sperm– Non-flagellated sperm
• Ovule = megasporangium– Contains egg– Retained w/ in parent tissue– After fertilization develops into seed
Seed
• From ovule• Contains embryo (young sporophyte)• Nutrients for embryo• Protects and disperses embryo• Important food source for animals, supported
evolution of faster, larger, more intelligent organisms.
Figure 30.3-3Immatureovulate cone
Integument (2n)
Megaspore (n)
Spore wall
Megasporangium(2n)
Pollengrain (n)Micropyle
(a) Unfertilized ovule (b) Fertilized ovule
Malegametophyte (n)
Pollen tube
Dischargedsperm nucleus(n)
Egg nucleus(n)
Femalegametophyte (n)
Seed coat
Sporewall
Foodsupply(n)
Embryo (2n)
(c) Gymnosperm seed
Figure 30.UN05
Five Derived Traits of Seed Plants
Reducedgametophytes
Heterospory
Ovules
Pollen
Seeds
Malegametophyte
Femalegametophyte
Microscopic male andfemale gametophytes(n) are nourished andprotected by thesporophyte (2n)
Microspore (gives rise toa male gametophyte)
Megaspore (gives rise toa female gametophyte)
Ovule(gymnosperm)
Integument (2n)
Megaspore (n)
Megasporangium (2n)
Pollen grains make waterunnecessary for fertilization
Seeds: survivebetter thanunprotectedspores, can betransportedlong distances
Seed coat
Food supply
Embryo
Flowering Plants (angiosperms)
Dog rose (Rosa canina), a wild rose
Angiosperm developments
• Flowers– Promote effective, targeted reproduction– Transfer of sperm to egg– Attract w/ sight and smell– Reward w/ food (pollen and/or nectar)
• Fruit– Protects and disperses seed more effectively
Tomato
Ruby grapefruit
Nectarine
Hazelnut
Milkweed
▼
▼
▼
▼
▼
Figure 30.11c
Seeds within berries and otheredible fruits are often dispersedin animal feces. The barbs of cockleburs facilitate
seed dispersal by allowing the fruitsto “hitchhike” on animals.
Angiosperm Diversity: monocots v. dicots
Embryos Leaf venation Stems
MonocotCharacteristics
Onecotyledon
Veins usuallyparallel
Vascular tissuescattered
Root systemusually fibrous(no main root)
Pollen grainwith oneopening
Floral organsusually inmultiplesof three
Floral organsusually in
multiples offour or five
Pollen grainwith threeopenings
Taproot(main root)
usually present
Vascular tissueusually arranged
in ring
Veins usuallynetlike
Twocotyledons
EudicotCharacteristics
Roots Pollen Flowers
Figure 30.2PLANT GROUP
Seed plants (gymnosperms and angiosperms)
Reduced (usually microscopic), dependent onsurrounding sporophyte tissue for nutrition
Dominant
Gymnosperm Angiosperm
Microscopic femalegametophytes (n)inside ovulate cone
Microscopic femalegametophytes (n)inside these partsof flowers
Microscopicmalegametophytes(n) inside pollencone
Microscopicmalegametophytes(n) inside these partsof flowers
Sporophyte(2n)
Dominant
Sporophyte(2n)
Reduced, dependenton gametophyte fornutrition
Gametophyte(n)
Example
Sporophyte
DominantGametophyte
Mosses and othernonvascular plants
Ferns andother seedlessvascular plants
Reduced,Independent(photosyntheticand free-living)
Gametophyte(n)
Sporophyte (2n) Sporophyte (2n)