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49 Cards in this Set

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Auxins
-The first plant hormone discovered

-Found in seed embryos, maristems of apical buds, and young leaves

-growth phenomena

-stimulates cell elongation, root growth, cell differentiation and branching, regulates development of fruit, enhances apical dominance, functions in phototropism and gravitropism, promotes xylem differentiation, and retards leaf abscission
Gibberellins
-Found in maristems of apical buds and roots, young leaves and embryos

-Promotes seed and bud germination, stem elongation and leaf growth, stimulates flowering and development of fruit, and affects root growth and differentiation
Ethylene
-Found in tissues of ripening fruit, nodes of stems, and aging leaves and flowers

-Also produced naturally

-Promotes fruit ripening, opposes some auxin effects, promotes or inhibits growth and development of roots, leaves and flowers, depending on species.
Plant sensory systems
-Plants possess surprisingy sophisticated systems for responding to environmental conditions like: light, gravity and touch
Plant responses involve
-receptors and hormone-mediated signal transduction

-they rely exclusively on chemical messengers
Blue light sensory system
-Receptor: NPH1 in stems and leaves; light spectrum; short wave length

-Signal Transduction:NPH1 autophosphorylates; the remainder of system is unknown, but involves CRY1 and CRY2 proteins

-Response: Phototropism occurs

-Adaptive Value: Stems grow toward lights with wavelengths needed for photosynthesis
Red Light sensory system
-Receptor: Phytochrome in seeds and elsewhere

-Signal Transduction: Phytochrome changes to Pfr form and activates response

-Response: Seed germinates

-Adaptive Value: Sunlight triggers sprouting in species that require full sun
Far-red light sensory system
-Receptor: Phytochrome in stem

-Signal Transduction: Phytochrome changes to Pf form and induces responser; mechanism is unknown

-Response: stems lengthen

-Adaptive Value: Species that require full sun attempt to escape shade
Gravity sensory system
-Receptor: Integrin proteins located in cell membrane or in amyloplast membrane?

-Signal Transduction: Details unknown, but auxin is involved

-Response: Cells on opposite sides of root or shoot elongate; tissue curves

-Adaptive Value: Roots grow down; shoots grow up
Highlights in plant evolution
-Land plants evolved from green algae

-Closest relatives are charophyceans (freshwater green algae)
What is a land plant?
-Eukaryotic
-multicellular
-possess chloroplasts in addition to mitochondria
-exhibit alternation of generations
What is a land plant? continued...
-Blue-green algae aka cyanophytes
-prokaryotes engulfed by plants for photosynthetic activity
-shared, derived characteristics include: haploid gametes, but no adults; alternate haploid/diploid stages
rRNA sequences
-ribosomal RNA
-everything but viruses have them
-can find homological sequences
-used extensively
Bryophytes
-non-tracheophyte plants with protected embryos
• lack phloem and xylem
• includes liverworts, hornworts and mosses
• require water for reproduction; confined to wet environments
-sporophyte dependent on gametophyte
Seedless, vascular plants
-Possess cells joined into tubes that transport water (xylem) or nutrients (phloem)
• includes lycophytes (club mosses), ferns and horsetails
• require water for fertilization
-Large sporophyte, small, independent gametophyte
Seed plants
• evolution of seed a major advance in occupation of
terrestrial habitats
• seed is a sporophyte embryo packaged along with a
protective coat
-Reduced gametophyte dependent on sporophyte
Gymnosperms
-"naked seeds"
– lack enclosed chambers (ovaries) in which
angiosperm seeds develop
– includes cycads, ginkos, conifers: pines, firs,
redwoods
Angiosperms
-flowering plants
– most diverse and economically important
– double fertilization with triploid endosperm
Gametophyte
-haploid multicellular organism (n)
-produce gametes by mitosis
Sporophyte
-diploid multicellular organism (2n)
-produce spores by meiosis
Spore
develops directly into adult
Gamete
must combine with other gamete to form zygote
Liverworts, hornworts, mosses
-non-vascular plants
-18,600 species
Lycopods, horsetails, ferns
-vascular, but seedless
-13,015 species
Gymnosperms
-seed plants
-721 species
Angiosperms
-flowering seed plants
-250,000 species
-abundant, diverse, comparable to animal lineages
Challenges of living on land
-threat of dessication
-transporting water through the plant body
-establishing an upright body to compete for sunlight
-transporting gametes without water
Advantages and adaptations of living on land
-Sunlight and CO2 more available
-cuticle and stomata
-vascular tissue
-lignin in cell walls and an erect growth habit
-reduced gametophytes; male gametophyte travels to female as pollen
-specialized methods of photosynthesis: C4 and CAM
Stomata
-pores on leaf surface
-restrict water are to water loss
Lignin
-produces wood
-allows for skeleton of plant and height
C3 photosynthesis
-most plants have it
-with water
C4 carbon intermediate photosynthesis
-grasses have modification
-conserve water
CAM photosynthesis
-succulent plants
-open stomates at night instead of day when temps. is low and humidity is low
-take in CO2 and use it during day
Double fertilization
-pollen tube discharges two sperm into female gametophyte within ovule
Angiosperm life cycle
-double fertilization occurs
-one sperm fertilizes egg while other combines with two nuclei in central cell of female gametophyte and initiates development of food-storing endosperm
-endosperm nourishes developing embryo
Angiosperm life cycle continued...
-sporophyte-dominant
-gamtophytes:
female-ovule
male-pollen grains are haploid (produces gametes through mitosis)
Plant adaptations continued...
a) Wings enable maple fruits to be easily carried by the wind eg. sycamore (maple) seeds

b)seeds within berries and other edible fruits are often dispersed in animal feces

c)the barbs of cockleburs facilitate seed dispersal by allowing these fruits to hitchhike on animals

d)plants have lost of mold; many chemicals produced by plants to inhibit mold growth

e)fleshy fruits adapt to increase attractiveness to animals
Most of our food comes from...?
angiosperms
Products from seed plant are...
important to human productivity
Which 6 crops yield 80% of the calories consumed by humans?
wheat, rice, maize, potatoes, cassava, and sweet potatoes
USA is a nation of
-CORN!
-most food produced in US is derived from a cornfield in Iowa
-corn has distinctive C13 profile on mass spectrophotometer
In a fast-food meal...
soda: 100% of carbon from corn
burger: 56% of carbon from corn
Animals
-most exhibit determinate growth, meaning the growth of indiv. ceases when adult stage is reached
Plants
-growth is indeterminate, meaning indiv. continues to grow after adult stage is reached
-growth is generated by specific regions of active cell divisions called meristem
meristem
groups of cells that retain ability to produce new organs indefinitely
All plant organs arise from...?
cell divisions in meristem
Animals 2
• Germ-line sequestered early in development in most animal groups(exceptions include cnidarians)
• Cells lose totipotency early due to differentiation
• Mutations in somatic cells not transmitted to offspring
Plants 2
• Meristem is perpetually embryonic tissue (retains totipotency)
• Mutations that occur in meristem during development of individual can be transmitted to offspring
• Restricted case of the evolution of acquired characters
-can live thousands of years
Cnidarians
-corals, anemones, hydras, and jelly-fishes
-dont have early germ-line sequences