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Describe the signal transduction pathway in plants.
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What do plant hormones coordinate?
- -hormones = chemical signals that coordinate the parts of an organism
- - coordinates:
- -growth
- -development
- -responses to stimuli
- -affect division, elongation, cell differentiation
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Where are the following plant hormones produced and what do they effect: auxin, gibberellin, cytokinin, abscissic acid, ethylene
- Auxin-stem apex, young leaves
- -expanding tissues= cell elongation
- -roots = initiates lateral roots
- -axillary buds = inhibits growth(apical dominance)
- -cambium = promotes xylem differentiation
- -leaves, fruits - inhibits abscission
- -developing embryos
- -ovary = promotes fruit development
- Gibberellin
- -stem apex, young leaves
- -stem internode = promotes cell division, cell elongation
- -embryo
- - seed = promotes germination
- -embryo (grass)
- -endosperm = promotes starch hydrolysis
- Cytokinin
- -root apex
- -stem apex, auxiliary buds = promotes cell devision (release of apical dominancy)
- -leaves = inhibits senescence
- abscissic acid
- -leaves
- -guard cells = closes stomata
- -stem apex = promotes dormant bud formation
- -ovule
- -seed coat = inhibit seed germination
- ethylene
- -wounded tissues, aged tissues
- -stem = inhibits cell elongation
- -leaves = promotes senescence
- -fruits = promotes ripening
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What is leaf abscission?
- Leaf Abscission-change in balance of auxin and ethylene controls leaf abscission
- -auxin produced by leaf blade maintains petiole connection
- -ethylene produced by damaged tissue -> activation of genes to synthesize chlorophyllases and proteases
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What is photoperiodism and what are some plant events that involves?*
- -photoperiodic receptor, is located on the leaf
- -think of the leaf masking experiment
- -photosynthesis cannot occur
- -plant events
- -photoperiodic control of flowering serves an important role to synchronize the flowering of plants of the same species in a local population
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How do "long-day" and "short-day" plants utilize light to initiate flowering? How does exposure to red/far-red light during nighttime influences this process?
- -long day plants have short night
- -short day plants have long nights
- -if the night is interrupted, the flowering signal would disappear.
- -red light was most effective at breaking the night stimulus
- -effect was reversed by far red light
- -indication that the photoreceptors involved in flowering is phytochrome
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Give examples of how plants respond to the following environmental cues (mechanical, gravity, flooding, drought, salt).
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Understand the angiosperm life cycle (include: male gametophyte, pollen, ovule, megasporangium, ovary, meiosis).
- male-microspore->microsporocyte->microsporangia
- -sperm-> pollen tube -> pollen
- female
- -megaspore->megasporocyte->megasporangia
- -ovule->seed w/seed coat
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Describe the 4 major parts of the flower and the function of each. How do complete flowers differ from incomplete flowers, staminate from pistillate and monoecious from dioecious?
- 4 parts of flower-sepals
- -petals
- -stamen
- -pistil
- complete vs incomplete-complete has 4 main flower parts
- -incomplete:
- -lacks 1+ flower part
- -only has either female or male parts
- staminate vs pistillate-staminate (stamen bearing) = male
- -pistillate (pistal bearing) = female
- monoecious vs dioecious-mono =staminate and pistillate flowers on same plant
- -di = staminate and pistillate flowers on separate (2) plants
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What type of evolutionary specialization do we see in flowers of the core angiosperms?
- flowers with:
- -reduced and fused petals/sepals
- -inferior ovaries
- -receptacle fused to ovary
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Describe abiotic and biotic mechanism for pollination
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What is double fertilization in angiosperms and why is it so important? Describe mechanisms that prevent self-fertilization in plants
- Prevent double fertilization-dioecious
- -mechanical (pin vs thrum flowers, blocked access)
- -self-incompatability: pollen rejected with S-gene matching an allele in stigma
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Describe major clades of the anthophyta (angiosperms).
- -Basal angiosperms
- -magnoliids
- -monocots
- -eudicot
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How does the seedling hypothesis explain the dominance of angiosperms over gymnosperms?*
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Compare/contract seed germination in monocots and typical eudicots
- Compare
- -as seed matures, dehydrates and enter dormancy
- -seed dormancy increases chances of germination at optimal time and place
- -breaking of seed dormancy
- -often involves environmental cues (temperature or light)
- -imbibition = uptake of water
- Contrast
- -eudicot germination
- -radicle is first part to emerge
- -a hook forms in hypocotyl, which is pushed above ground with growth
- -monocot germination
- -coleoptile pushes upward through the soil and into the air
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How does simple differ from compound fruit (aggregate or multiple)? Describe mechanism of seed dispersal.
- -simple fruits typically have 1 seed or 1 defining feature
- -compound fruits have several of one feature
- -ie single flower but several pistils
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What are some mechanisms for asexual reproduction in plants?
- -vegetative reproduction
- -apomixis
- -production of seed asexually without fertilization
- -fragmentation
- -separation of parent plant into parts that develop into whole plants
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Name some ways in which we depend on plants
- -food
- -fuel
- -wood products
- -medicine
- -modern crops are products of relatively recent genetic change resulting from artificial selection
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What is artificial selection and how has it been used extensively for crop plants?
- -Natural selection has acted on the plant body plan to produce a remarkable diversity of plant forms.
- -Artificial selection by humans on the plants that provide us with food and fiber has greatly altered plant form as well.
- -used extensively for crop plants in order to boost beneficial features for output
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Describe some benefits and costs of genetically modified plants
- benefits
- -can further maximize the crops potential
- cost
- -superweeds resistant to hericides
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