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71 Cards in this Set
- Front
- Back
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etiolation |
the morphological adaptions for growing in darkness |
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horologium florae |
floral clock, created by Carolus Linnaeus |
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What does etiolation provide? |
this adaption enables the shoots to break ground before the nutrient reserves in the tuber are exhausted. |
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de-etioltion |
when a plant reaches light "greening" stem elongation slows; leaves expand; roots elongate and the shoot produces chlorophyll |
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explain de-etiolation in terms of the signal transduction pathway |
light is transduced into a response (greening) phytochrome acts a the receptor proteins |
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phytochrome |
a member of a class of photoreceptors located in cytoplasm a receptor --a protein that changes shape in response tospecific stimuli |
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Reception in plants |
signals are detected by phytochrome in cytoplasm |
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Transduction in plants |
involves second messengers - Ca^2+ and cGMP
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Calcium ions in transduction |
cytosolic Ca ion levels are usually low phytochrome activation leads to Ca ion channels openning and Ca ions increas in cytosol |
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cGMP in trasduction in plants |
phytochrome activates guanylyl cyclase (guanylyl cyclase produces cGMP) |
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How can enzymes enhance the signaling pathway in biochemical pathways? |
post-translational modification transcriptional regualtion |
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post-translational modification |
activates pre-existing enzymes modified by the phosphorylation of specific Amino acids - which alters the proteins hydrophobicity and activity. |
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transcriptional regualtion |
increases or decreases the synthesis of mRNA encoding a specific enzyme by transcription factors
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What do most second messengers do? |
activate protein kinases directly (post-translational modifcation) holds true for cGMP and Ca ions |
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protein phosphatases |
enzymes that dephorylate specific proteins they are important in the "switch off" process |
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transcriptional regulation in de-etiolation |
transcription factors are activated by phosphorylation in response to light
"the activation of these transcription factors depends on the phosphorylation by protein kinases activated by cGMP or Ca ions" |
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activators |
increase transcription of specific genes |
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repressors |
decrease transcription of specific genes |
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hormone original meaning |
signal molecule that is produced in tiny amounts by part of an organisms body and transported to other parts, where it binds to a specific receptor and triggers responses in target cells and tissues animals = circulatory system |
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difference between plants and animal hormones |
no circulatory system can act locally there are other things that are similar aka sucrose so we call them plant growth regulators |
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plant growth regulators |
organic compounds natural or synthetic that modify or control specific physiological process within a plant |
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tropism |
growth response in plant organisms that results in curving toward/away from a stimuli |
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phototropism |
growth of a shoot toward/away the light "positive or negative" |
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Charles and Francis Darwin Experiment |
only the tip of coleoptile sense light phototrophic bending at a great distance from the site of light perception therefore, the signal must travel towards |
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Peter Boysen Jensen Experiment |
the signla for the bending is a light activated mobile chemical (since travels through a permeable barrier) |
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Fritis Went experiment |
extracted the chemical messenger the agar block contained a chemical produced in the coleptile tip he named it auxin IAA indoleacetic acid |
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What cause coleoptiles to grow towards light? what about non-coleoptiles |
coleoptiles- asymmetrical distribution of auxin dark side has higher concentration non-coleoptiles have no auxin |
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What is the major natural auxin in plants? |
IAA indoleacetic acid |
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Where is auxin produced? |
in shoot tips and it is then transported from cell to cell down the stem it only travels from tip to base unidirectional aka "polar transport" exits the basal end and enters the apical end |
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How does auxin work? |
acid growth hypothesis auxin stim. plasma membrane proton pumps increase voltage across membrane (increased membrane potential) lowers pH of cell wall expansins-acidification of cell wall. loosens the wall increase membrane potential enhances ion uptake, there4 osmatic uptake and increase tugor and cell wall plasticity therefore cell enlongates |
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What does auxin do? |
stem elongation alters gene expression pattern formation/spatial organization phyllotaxy development of fruit direscts the pattern of leaf veins vascular cumbium (woody tissue) organization of female gametophytes vegetative propagation herbicides gravitopism/phototropism promotes the formation of lateral and advenitious roots enhance spical dominance promotes vascular differentiation retards leaf abscission |
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Cytokinins |
cell division in shoots and roots modify apical dominance promote lateral bud growth movement of nutrients into sink tissue stimulate seed germination delay leaf senscence differentiation anti-aging and slows apoptosis
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where is cytokinin produced? |
actively growing tissue (roots embryo and fruit) move up plant by xylem sap |
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callus |
a cluster of undifferentiated cell as a result of cytokinin without auxin. both are needed |
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apical dominance |
the ability of the apical bud to suppress the development of auxillary buds |
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Gibberelins |
stem elongation (by enhancing stem enlongation and cell division) fruit growth seed germination |
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Where is gibberelin produced |
young roots and leaves |
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Abscisic acid |
seed dormancy drought tolerance slows growth |
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Strigolactones |
seed germination help control apical dominance help establish mycorrhizal association (attraction of mycorrhizal fungi to the root) |
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What does ethylene do? |
promotes ripening of fruit leaf abscission triple response enhances the rate of senescene promotes root formation
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When does ethylene act? |
in response to stress mechanical pressure, drought, flood, injury, infection |
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triple response |
enables a shoot to avoid an obstacle slowing of stem enlongation thickening of stem curvature of stem-horizontally
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senescene |
programmed death of certain cells or organs or entire plant |
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photomorphogenesis |
the effects of light on plant morphology ex. photosynthesis, trigger growth and development, measure passage of days and seasons |
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Action spectrum |
a graph that depicts the relative effectiveness of different wavelengths of radiation in driving a particular process |
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What are the most important colors in photomorphogenesis |
red and blue
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What are the two major classes of light receptors |
blue light photo receptors phytochromes (red light) |
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Blue light photo receptor responses |
phototropism light induced opening of stomata light-induced slowing of hypocotyl elongation (when a seed breaks ground) |
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three pigments that detect blue light |
cryptochromes-inhibition of stem elongation Phototropism-protein kinase -phototropic curvatures zeaxanthin-stomatal opening |
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Phhytochromes |
de-etiolation seed germination shade avoidance
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U.S Department of Labor |
red light stimulates germination far red light inhibits germination final light exposure is the determining factor the effects of red and far red are reversible |
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phytochrome structure |
has two identical subunits polypeptide component covalently bonded to non polypeptide chromophore (the light absorbing part of the phytochrome subunit) |
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chromophore |
the light absorbing part of the phytochrome subunit photoreversible between two isomeric forms
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How does the switching mechanism of the phytochrome work? |
absorption of red light causes the Pr to change to Pfr. absorption of far red light causes the Pfr to change to Pr. Pfr form of the pigment switches on physiological and developmental responses in the plant |
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What controls light induced events in plants |
the pr to pfr interconversions |
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Which is faster Pr --> Pfr Pfr --> Pr |
Pr--> Pfr |
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Germination and light exposure |
the ratio of Pfr to Pr increases in sunlight and the production of Pfr triggers germination |
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Shade avoidance and sunlight |
direct sunlight increases Pfr= branching and inhibits vertical growth lack of sunlight increases Pr = vertical growth?
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Circadian rhythms |
cycles that have a frequency of about 24 hours and not directly controlled by an environmental variable |
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Free-running periods |
when circadian deviates when plant is in controlled environment varies 21-27 hours they still keep perfect timing but they are not synchronized with the rest of the world |
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What is the cause of carcadians? |
oscillations in transcription of certain genes makes about 5% of mRNA |
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What produced the oscillations? |
negative feedback loops and time delays |
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How do plants measure the passage of day and night in nature? |
interactions in phytochrome and biological clock |
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photoperiodism |
the physiological response to the relative lengths of night and day example - flowering |
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Short day plants/ long night plants |
require a light period of shorter than a critical length has a minimum length for night examples: tobacco, chrysanthemums, poinsettias, soy bean, usually bloom late summer, fall, or winter
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long day plants/ short night plants |
has a maximum length for night examples: spinach, radishes, lettuce, irises, cereal bloom late spring/early summer |
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What light is most effective in interrupting nighttime of photoperiod |
red light |
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vernalization |
the use of pretreatment to cold to produce flowering |
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florigen |
hypothetical signaling molecule for flowering if one leave detects proper photoperiod conditions, the whole plant flowers if all leaves are removed, insensitive flowers |
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How does florigen work? |
Macromolecule moves by symplastic via plasmodesmata it regulates plant development
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flowering locus T |
a gene that is activated in leaf cells during conditions favoring flowering it travels through symplasm to the shoot and initiates flowering |
