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88 Cards in this Set
- Front
- Back
Growth
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irreversible increase in mass, cell division and cell enlargement/expansion
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Differentiation
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change from generalized cell type to specialized one with specific functions
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Development
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Growth + Differentiation
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Open Growth
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continue to initate new organs through lifespan
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Totipotency
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single differentiated cell can de-differentiate and behave like zygote to give rise to whole new plant
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Cloning Plants, what was used?
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Carrot root phloem cells behave like zygotes. Regenerate whole fertile carrot plants - genetically identical to original one.
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Callus
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Mass of undifferentiate cells, can propagate forever
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Steps of cloning plants?
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Differentiated Cells --> Callus --> Roots/Shoots --> Entire Plantlet
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Medium used cloning plant?
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Coconut Milk, rich in cytokinins
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What are the 3 values of tissue culture?
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1. Propagate individual plants while maintaining desirable traits/genomes (orchids, etc)
2. Develop new genotypes with desired traits = genetic engineering, cloning 3. Study genetics of somatic cells (instead of germ cells). |
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How old are bristlecone pines in Southern California?
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5,000 years old
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Axillary bud
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Pocket of meristematic cells left behind (also vascular cambium). They remain undifferentiated.
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Zone of cell division
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Meristem (shoot & root apical meristem)
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After zone of cell division comes..
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zone of cell division = meristem
zone of cell elongation cell differentiation further away from apical meristem |
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Cell Cycle of Cell Division
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Cell Cycle = phases of DNA synthesis and division. G1, S, G2, M.
From the G0 --> G1 phase, plant growth hormones (cytokinins) to stimulate cell division to cause them to break dormancy and re-enter cell cycle |
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What is the driving force for plant cell growth?
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Turgor pressure and osmotic properties
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2 effects of H+ ions pumped into cell wall by H+/ATPases.
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Since lower pH
1) weakens interactions between wall components (pectins, cellulose) 2) stimulate expansins (proteins involved in wall loosening). Some plant growth hormones stimulate cell enlargement or elongation (auxin) |
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When does cell differentiation occur?
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Occurs after cell division (and enlargement/enlongation)
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Can cell division be involved in differentiation?
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Yes, asymmetric cell division creates trichome and elongated epidermal cell.
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What are the two types of regulation of gene expression?
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Temporal (time) and Spatial (space)
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4 examples of spatial gene expression
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1. every cell type, housekeeping genes
2. cell specific 3. tissue specific 4. organ specific |
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Temporal gene expression patterns
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Constituitive - "on" all the time
Regulated/modulated. inducible, repressible, rhythmic. |
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5 places where developmental regular of genes occurs
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1. transcription - always
2. mRNA stability/degradation 3. translation 4. protein stability/degradation 5. post-translational modification (phosphorlyation) |
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Why are microarrays so important?
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Permit genome-wide gene expression studied in every gene. Have a bank of all the possible genes. Can find out what genes are expressed
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Microarray steps
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1. from the plant, make cDNA, incorporate fluorescent. labels the nucleotides.
2. digest RNA to generate single stranded cDNA. 3. hybridize to microarray. if it matches, it will bind to the microarray. if not, it will wash away. The microarray shows what genes were being expressed. |
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What is the strategy for finding key regulatory genes in development?
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Genetic Approach.
1) identify/isolate developmental mutants of a model genetic organism 2) map and clone the gene 3) study gene's structure and function |
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Homeotic Genes
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Genes that control overall body plan of an organism. Have common homeobox sequence ( ~180 bp)
Homeotic genes determine organ identity. |
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Why is arabidopsis thaliana a model plant system?
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Small organism, short reproductive cycle, n = 5.
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Flower Development. 4 whorls. 3 classes of homeotic genes (A,B,C). What makes up the 4 whorls and to which genes are they correlated with?
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Sepal (A), Petal (A,B), Stamen (B,C), Carpel(C)
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If knockout B, what is expressed?
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Only A & C. So only Sepals (A) and carpels (C)
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Developmental response
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Environmental signals/stimuli elicit responses through signal transduction mechanisms
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Vernalization
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need prolonged cold period for seed germination or flowering.
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Gravity Responses
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Another developmental response to the environment, roots grow towards earth. Shoots grow away from it. Pattern of roots depend on which one successful in encountering water.
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Thigmotropism - Touch Responses
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Touch - developmental response. Tendrils twine around supports, thigmotropism is change in rate of growth of one side vs other, or rapid change in turgor to fold leaves.
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Light Responses
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Photomorphogenesis - presence of light - controls development (leaves, greening)
Phototropism - controls direction of growth (towards/away) Photoperiodism - controls flowering short day plants (fall > flower as days) long day plants (flower as days . some length (late spring) day neutral - something else regulated flowering, sometimes need more than one signal (short days & cold before flowering) |
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3 system component to responding to light
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1. Photoreceptor - detects light
2. Signal transduction system - secondary messengers. transmit and amplify signal. 3. Response system - gene activation. |
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Plants respond to light by... (4)
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1. presence
2. quality of wavelength 3. Duration and quantity (daylength) 4. direction |
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Examples of photosynthetic and accessory pigments
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Chlorophylls, Carotenoids, Xanthophylls, Anthocyanins
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Major Photoreceptors: Phytochrome (Phy)
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absorbs red(660)/far-red (730nm) light. determines daylength and shading (quality of wavelength) The 2 are interconvertible.
red - active, useable for photosynthesis far-red - longer wavelengths not useable, tells the leaves they are in shade. |
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Far Red
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Not useable in photosynthesis, tells the leaves they are in the shade.
Hydrophobic - binds membranes better.Is the active form since it is what is converted to the red form |
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Cryptochrome
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absorbs blue light (350-450 nm). Role in floral initiation and circadian rhythms.
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Roles of Phytochrome
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1. Stem Elongation in young seedlings - emergence from soil
2. seed germination - seasonal 3. Promoting stomatal openings |
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Phototropin (PHO)
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abosrbs blue light.
phototropism is growth twards light, similar to cryptochorme - has a FMN and also kinase activity. |
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Chromophore
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a flavin (FAD). flavin adenine dinucleotide.
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LOV domains
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in genes responding to light, oxygen, voltage. In phytochrome and cryptochrome
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Signal Transduction Mechanisms
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1. cGMP
2. calmodulin - binds 4 Ca+ ions to become activated. Increase Ca by influx or release from internal stores. 3. trimeric G- proteins. Becomes activated when binding GTP, beta and gamma unit dissociate, alpha moves to targets. Uses the GTP to release from binding site, three parts come back together. |
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3 Photoreceptors
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1. Phytochrome (red 660, far red - 730). determine daylight and shading
2. Cryptochrome - blue light.floral initiation and circadian rhythm 3. Phototropin - absorbs blue light. Growth towards light. |
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4 Whorls
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Sepal, Petals, Stamen, Carpals
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Hormones
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chemical produced in one part of body that has effects on another part
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Features of Hormones (4)
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1. Act in small quantities, very potent/effective
2. Released into plant circulatory system - mostly phloem 3. Target cells/tissues - receptors for the hormones 4. Binding triggers response in target cells. |
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5 Classes of Major Plant Hormones
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Auxins, Cytokinins, Gibberellins, Abscisic Acid, Ethylene
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Auxin redistributed to shaded side bends more than?
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Shaded side bends more than sunny side.
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Auxin produced where?
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Auxin produced in shoot apex and leaf tips. From tryptophan, moves down through plant and has effects on target tissues. Shoot apex and leaf tips. IAA and NAA. Indole acetic acid and a-naphthalene acetic acid (synthetic)
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What are the forms that auxin exists in?
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Auxin exists in free form or conjugated to amino acids/sugars (inactive)
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Agent Orange
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defoliant/herbicide. also contained dioxin (teratogen - birth defects)
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Auxin: acid growth hypothesis
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Auxin binds to receptor, activates pumps to pump H+ out to cell wall, pH drops, activates expansins for cell elongation.
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Auxin: statocytes and statoliths
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Statocytes in the root cap, inside the statocytes, statoliths have amyloplasts (colorless chloroplasts that store starch). The statoliths are heavier than cytoplasm so they sediment to lower side of the cell.
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What happens when room is shifted to horizontal?
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If shifted to horizontal, statoliths think that are in contact with the membrane-bound receptor molecules, to compensate since they think auxin is on the bottom, the statoliths trigger auxin redistribution to the lower side of the root. Greater concentration of auxin on the lower side of root INHIBITS cell elongation, so root bends downward.
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Apical Dominance
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Axillary buds delay outgrowth until they are some distance away from the shoot apical meristem. Auxin from the shoot apical meristem inhibit outgrowth, cytokinins promote bud outgrowth.
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Auxin Effects
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1. Promotes cell elongation, important in phototropism and gravitropism, apical dominance.
2. Basipetal movement in the spring activate the Vascular Cambien for cell division and differentiation in the xylem. 3. Leaflet initiation in compound leaves 4. Gametophyte patterning - egg cell identity. |
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What does auxin help with?
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1. Helps a cell determine where it is relative to other cells.
2> Helps a cell deterime where it is relative to the shoot apex. 3> Determining morphology if conditions change |
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Cytokinins
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Purines, variation of adenine. Zeatin and Isopentenyl adenine. Kinetin - synthetic.
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Where are cytokinins produced?
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Room meristems
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seven funnctions of cytokinins
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1. promote cell division in target cells, apical meristems and maintence of meristems.
2. promote axillary bud outgrowth 3. balance root/shoot growth 4. seed development 5. may delay senescence in leaves. 6. stimulate VC with cell differentiation 7. Activate root nodule formation. High aux: stimulates root development Low aux: cyt: shoot development |
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Gibberellins
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GA3 - most common
GA1,3,4 - active forms in plants ring structure |
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Where are gibberellins produced?
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Upper most leaves
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4 functions of gibberellins
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1. cause cell division and stem elongation
2. growth and differentiation in the V.C. with phloem 3. Transition from vegetative to reproductive state 4. Promote seed germination to stimulate embryo to renew development. Stimulate embryo development, increase a-amylase activity which breaks down starch as sugar for the growing plant. |
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How to gibberellins work?
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Promote cell wall extensibility - some cells not responsive to auxins, but respond to GA.
2. Modulate gene expression - cambium and seeds. Unbound state, DELLA protein inhibits transcription, bindng to transcription factor. GA binds to receptor, DELLA degraded and a-amylase produced. GA acts as a de-pressor for amylase. |
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Absisic Acid - produced where?
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leaves and dry roots (prepare ABA for drought)
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2 Functions of Absisic Acid?
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1. promote dormancy in seeds - antagonist of GA
2. associated with plant stress response (aka, in leaves and dry roots for drought). closes stomates, wilting leaves, cells release aba. |
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Ethylene, produced where?
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A volatile gas, produced locally.
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Functions of ethylene?
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1. Fruit ripening, positive feedback. Climateric - sudden increase
2. Leaf abscission - decrease in auxin in the shoot, ethylene produced. Ethylene inhibits auxin transport, further decreases auxin. Less auxin produces more ethylene and degradative enzymes. Changes in cell walls in abcission zone, leaf drops. Causes induction of corky cells at the site of abscission which seals wound and leaf scars. |
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Things ethylene fixes
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low ph --> kinase neutralize acid --> sweeter
chlorophyll (green) --> hydrolases break down chl --> color stands out start --> amylases --> sweeter Pectin --> pectinases --> softer fruit Large organics --> hydrolases --> sweet smelling aromatics |
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Brassinosteroids
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promote cell elongation, reduce stress from injury, xylem development
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Jasmonic Acid
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resist fungal infection and other stresses
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Salicylic Acid
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perception of pathogen attack
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Systemin (polypeptide)
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internal signaling of wounds
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Azelaic Acid
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accumulates in sap and confers local and system resistance against a pathogen. Primes plants to accumulate salicyclic acid
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Strigolactones
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inhibit shoot branching and involved in root communication with mycorrhizal fungi
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Paclitaxel (taxol)
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used as anti-cancer drug from Yew trees. Add methyl jasmonate to cell cultures to increase amount of taxol produced.
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Acetylsalicylic acid
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aspirin!
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Minerals
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naturally occuring INORGANIC elements and compounds
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Criteria of essentiality of minerals
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1. are necessary for normal development and reproduction through a full life cycle. (absence of mineral prevents normal growth or reproduction)
2. restoration of growth/reproduction occurs only with that element. no substitue will suffice 3. must be taken up by the plant and used internally. not working outside the plant. |
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Methods of determining essentiality
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1. study chemical composition of plants. (note, endodermis also has minerals plants don't need)
2. hydroponics , growing plants in defined minerals, no soil |
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How many essential mineral elements for plants?
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13
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Medium that vonSach's developed in 1860 had 6 mineral nutrients which were.
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Calcium, Potassium, Magnesium, Nitrogen, Phosphorus and Sulture
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Macroelements (30-1,000 mmol/g dry weight)
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Anions: Nitrogen (NO3-), Phosphorus (H2PO4) and Sulture (SO4)
Cations: Potassium (K), Calcium (Ca) and Magnesium (Mg+2) |
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Relative uptake of macroelements in wheat?
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N>K>P>Ca>Mg/S
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