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PLANTS
EVERYTHING YOU NEVER WANTED TO KNOW
BUT NEEDED TO FORTHE AP EXAM
2007-2008
DomainBacteria
DomainArchaea
DomainEukarya
Common ancestor
Kingdom: Plants
Domain Eukarya
• Land plants evolved from green algae
• Researchers have identified green algae called charophyceans as the closest relatives of land plants
Genetic Evidence• Comparisons of both nuclear and
chloroplast genes– Point to charophyceans as the closest living
relatives of land plants
Chara, a pond organism
(a)10 mm
Coleochaete orbicularis, a disk-shaped charophycean (LM)
(b)
40 µm
Figure 29.3a, b
Animal vs. Plant life cycle
diploidmulticellularindividual2n
diploidmulticellularsporophyte2n
haploidmulticellulargametophyte1n
haploidunicellulargametes1n
gametes1n
Animal Plant
alternation of generations
meiosis
fertilization
mitosis
mitosismitosis
fertilization
mitosis
no multicellularhaploid
meiosis
spores1n
zygote 2n
zygote 2n
Pollen• Pollen
eliminated the requirement for water for fertilization– spread through
wind & animal
Angiosperm: flowering plants
Anther
FilamentStamen
StigmaStyleOvary
Carpel
Sepal
Petal
Ovule
sepalspetals
Flower • Modified shoot with 4 rings
of modified leaves– sepals– petals– stamens
• male
– carpel• female stamens
carpel
adaptations through mutations
• The life cycle of an angiosperm
Figure 30.10
Key
Mature flower onsporophyte plant(2n)
Ovule withmegasporangium (2n)
Female gametophyte(embryo sac)
Nucleus ofdevelopingendosperm
(3n)
Dischargedsperm nuclei (n)
Pollentube
Male gametophyte(in pollen grain)
Pollentube
Sperm
Survivingmegaspore(n)
Microspore (n) Generative cell
Tube cell
Stigma
OvaryMEIOSIS
MEIOSIS
Megasporangium(n)
Pollengrains
EggNucleus (n)
Zygote (2n)
Antipodal cellsPolar nucleiSynergidsEgg (n)
Embryo (2n)
Endosperm(foodSupply) (3n)
Seed coat (2n)
Seed
FERTILIZATION
Haploid (n)
Diploid (2n)
Anther
Sperm(n)
Pollentube
Style
Microsporangium
Microsporocytes (2n)
GerminatingSeed
Anthers contain microsporangia.Each microsporangium contains micro-sporocytes (microspore mother cells) thatdivide by meiosis, producing microspores.1
Microspores formpollen grains (containingmale gametophytes). Thegenerative cell will divideto form two sperm. Thetube cell will produce thepollen tube.
2
In the megasporangiumof each ovule, themegasporocyte divides bymeiosis and produces fourmegaspores. The survivingmegaspore in each ovuleforms a female gametophyte(embryo sac).
3
After pollina-tion, eventuallytwo sperm nucleiare discharged ineach ovule.
4
Double fertilization occurs. One spermfertilizes the egg, forming a zygote. Theother sperm combines with the two polarnuclei to form the nucleus of the endosperm,which is triploid in this example.
5
The zygotedevelops into an
embryo that ispackaged alongwith food into aseed. (The fruit
tissues surround-ing the seed are
not shown).
6
When a seedgerminates, the
embryo developsinto a mature
sporophyte.
7
From Ovary to Fruit
• A fruit– Develops from the ovary– Protects the enclosed seeds– Aids in the dispersal of seeds by wind or
animals
Co-evolution: flowers & pollinators
Plant Structure, Growth, and Development
Figure 39.4
1 Reception 2 Transduction 3 Response
CYTOPLASM
Plasmamembrane
Phytochromeactivatedby light
Cellwall
Light
cGMP
Second messengerproduced
Specificproteinkinase 1activated
Transcriptionfactor 1 NUCLEUS
P
P
Transcription
Translation
De-etiolation(greening)responseproteins
Ca2+
Ca2+ channelopened
Specificproteinkinase 2activated
Transcriptionfactor 2
• An example of signal transduction in plants
1 The light signal isdetected by thephytochrome receptor,which then activatesat least two signaltransduction pathways.
2 One pathway uses cGMP as asecond messenger that activatesa specific protein kinase.The otherpathway involves an increase incytoplasmic Ca2+ that activatesanother specific protein kinase.
3 Both pathwayslead to expressionof genes for proteinsthat function in thede-etiolation(greening) response.
• The bending of a grass seedling toward light
–Begins with the plant sensing the direction, quantity, and color of the light
Figure 39.1
• Xylem
–Conducts most of the water and minerals
–Includes dead cells called tracheids
• Phloem
–Distributes sugars, amino acids, and other organic products
–Consists of living cells