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Describe the signal transduction pathway in plants.
What do plant hormones coordinate?
- -hormones = chemical signals that coordinate the parts of an organism
- - coordinates:
- -responses to stimuli
- -affect division, elongation, cell differentiation
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
- -stem apex, young leaves
- -stem internode = promotes cell division, cell elongation
- - seed = promotes germination
- -embryo (grass)
- -endosperm = promotes starch hydrolysis
- -root apex
- -stem apex, auxiliary buds = promotes cell devision (release of apical dominancy)
- -leaves = inhibits senescence
- abscissic acid
- -guard cells = closes stomata
- -stem apex = promotes dormant bud formation
- -seed coat = inhibit seed germination
- -wounded tissues, aged tissues
- -stem = inhibits cell elongation
- -leaves = promotes senescence
- -fruits = promotes ripening
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
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
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
Give examples of how plants respond to the following environmental cues (mechanical, gravity, flooding, drought, salt).
Understand the angiosperm life cycle (include: male gametophyte, pollen, ovule, megasporangium, ovary, meiosis).
- -sperm-> pollen tube -> pollen
- -ovule->seed w/seed coat
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
- complete vs incomplete-complete has 4 main flower parts
- -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
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
Describe abiotic and biotic mechanism for pollination
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
Describe major clades of the anthophyta (angiosperms).
- -Basal angiosperms
How does the seedling hypothesis explain the dominance of angiosperms over gymnosperms?*
Compare/contract seed germination in monocots and typical eudicots
- -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
- -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
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
What are some mechanisms for asexual reproduction in plants?
- -vegetative reproduction
- -production of seed asexually without fertilization
- -separation of parent plant into parts that develop into whole plants
Name some ways in which we depend on plants
- -wood products
- -modern crops are products of relatively recent genetic change resulting from artificial selection
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
Describe some benefits and costs of genetically modified plants
- -can further maximize the crops potential
- -superweeds resistant to hericides
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