Term
| How is the meristematic phenotypic plasticity controlled? |
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Definition
| Integration via plant hormones |
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Term
| Meristems are sites of environmental perception and can perceive light and nutrient status, true or false? |
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Definition
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Term
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Definition
Auxin
Cytokinins
Gibberellins
Ethylene
Abscisic Acid
Brassinosteroids
Salicylates
Strigolactones
Jasmonates |
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Term
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Definition
Naturally occuring organic substances which influence physiological processes at low concentrations
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Term
| What do plant hormones effect |
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Definition
| Growth, differentiation and development, stomatal movement, epinasty, apoptosis, stress response, basically everything |
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Term
| How do hormones coordinate? |
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Definition
Biosynthesis and metabolism
Hormone specificity (storage types, transport types, active types)
Hormone transport
Hormone receptor and signal transduction
Tissue localization (different receptors/signalling/target genes in different places) |
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Term
| What is conjugation in hormone regulation? |
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Definition
| Part of biosynthesis pathway: can temporarily store a hormone in an inert form, lead to catabolic breakdown or be the means for producing the active hormone |
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Term
| How are hormones transported? |
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Definition
Through the xylem or phloem
Across cellular membranes
Through regulated transport proteins |
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Term
| What are common methods of signal transduction in hormonal response? |
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Definition
| Phosphorylation cascades and targeted proteolysis |
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Term
| What downstream effects can occur through the hormone pathways? |
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Definition
| Changes in gene transcription, changes in other cellular activites like ion transport, proteolysis |
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Term
| What targets proteins for proteolysis |
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Definition
| Ubiquination from hormones binding to receptor |
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Term
| Downstream effects (hormone responses) can differ due to _____ |
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Definition
| Environmental conditions (light/dark) |
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Term
| What is the order of hormone action in plants? |
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Definition
| Biosynthesis, transport, reception, signal transduction, downstream effects |
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Term
| How do we test the roles of hormones? |
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Definition
Identify endogenous substance (hormone)
Quantify levels and correlate with timing and magnitude of response
Determine whether removal of hormones removes response (mutants)
Determine if exogenous hormones restores response |
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Term
| What trait increased yield in wheat plants around the start of the green revolution? |
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Definition
| Biosynthesis of GA mutant, meant more resources were allocated to roots and seed and less to internode length (dwarf mutant) |
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Term
| What controls hormone levels in plants? |
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Definition
| Biosynthesis, metabolism and conjugation |
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Term
| How many active hormones are there? |
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Definition
| One for each pathway (Bioactive GA = GA1) |
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Term
| How can we determine hormone specificity? |
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Definition
| Apply exogenous hormones to biosynthesis mutants, or look at correlative data between endogenous levels and phenotypic expectancy (endogenous GA20 does not correlate with internode length for le wheat mutants, evidence that GA1 and not GA20 is the bioactive GA) |
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Term
| How does auxin regulate gibberellin content (crosstalk)? |
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Definition
Enhances le gene expression (gibberellin biosynthesis) and suppresses SLN gene expression (GA20>GA29 biosynthesis).
Does this by regulating expression of biosynthetic genes, targeting same transcription factors and regulating levels of receptors |
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Term
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Definition
| Growing plants in darkness |
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Term
| When does crosstalk (or cross-regulation) occur in hormone activity? |
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Definition
| When two hormone pathways are not independent. It can be positive and additive or synergistic, or negative |
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Term
| What can hormonal crosstalk affect? |
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Definition
| Synthesis, transport or signaling pathway of another hormone |
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Term
| Two genetically identical plants give different very different hypocotyl lengths, as a result of different hormonal levels. What can cause this? |
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Definition
| Raising seedlings in dark or dim light vs strong light |
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Term
| In wild type plants, what occurs when the apical bud is removed (decapitated), and what regulates this process? |
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Definition
| Shoot branching, auxin inhibits it |
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Term
| How do auxin and strigolactone interact in shoot decapitation? |
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Definition
| Auxin represses CK and compliments SL production in intact plants. When decapitated allows CK to produce shoot growth. |
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Term
| Cell growth, division and identity (including differentiation) is controlled by hormones, usually targeting GA for positioning information, true or false? |
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Definition
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Term
| How do plants perceive light? |
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Definition
| Phytochrome (multiple light receptors), switch between two forms (Pr and Pfr) which absorb different wavelengths |
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Term
How does phytocrome interconvert?
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Definition
| Molecular flip from Red (Pr) biosynthesising into far red (Pfr), which then decays into Pr |
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Term
| What does PAR stand for? How does R:FR light ratio effect plant growth? |
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Definition
Photosynthetically Active Radiation
Interacts with different phytochromes to disrupt usual hormone pathways |
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Term
| What is a photoperiod and how is it measured? |
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Definition
| The length of the day, measured by Phytochrome B in plants |
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Term
| What are the types of phytochromes? |
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Definition
Type I: high concentrations in etiolated seedlings, reversible but very unstable in Pfr form (half life of 1 hour)
Type II: Green tissues mainly, relatively stable, present at low concentrations |
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Term
| What does a plants photoperiod affect? |
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Definition
| Vegetative development and reproductive development |
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Term
| What must plants undergo before they can flower? |
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Definition
| Phase change (prepares plant to repsond to internal and external signals such as light and temperature) |
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Term
| What is the flowering signal, where is it produced and where does it go? Is it transmissable through grafting? |
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Definition
| Florigen, generated in leaf, goes one way to the apex, yes |
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Term
| What are the genetically regulated pathways to flowering? |
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Definition
Light dependent pathway (photoperiod)
Temperature dependent pathway
Gibberellin dependent pathway
Autonomous pathway
Can rely on one pathway but all 4 can be present |
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Term
| What are short-day, long-day and day-neutral plants? |
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Definition
SD: flower when daylight becomes shorter than a critical length
LD: flower when daylight becomes longer
DN: flower when mature, regardless of day length |
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Term
| Photoperiodism is linked to photosynthesis and involves a signal transduction process, true or false? |
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Definition
| False, does involve signal transduction process but is independent from photosynthesis |
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Term
| Phytocromes regulate florigen levels, resulting in expression of LFY gene at the shoot apical meristem which tells it to switch over to flowering, true or false? |
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Definition
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Term
| CO (CONSTANS) mRNA serves what function? What regulates it's expression? |
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Definition
| To induce flowering, regulated by circadian clock and day length (phytochromes) |
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Term
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Definition
| Process of some plants that need a period of chilling before flowering (temperature dependant pathway) |
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Term
| The four flowering pathways lead to an adult meristem becoming a ____ meristem |
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Definition
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Term
| What are some examples of short-range and long-range transport of hormones? |
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Definition
SR: Symplastic (through plasmodemata), Transcellular (across membranes), apoplastic (in cell walls)
LR: Phloem, xylem, polar auxin transport |
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Term
| How does the phloem transport hormones in comparison to xylem? |
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Definition
Phloem moves source to sink (turgor pressure)
Xylem moves from roots to leaves via transpiration flow (high to low water potential) |
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Term
| What is the polar auxin transport model? |
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Definition
| Moves auxin through the plant via PIN proteins (chemiosmosis) Based on the pH difference between the apoplast (5.5) and the cytoplasm (7), auxin gets deprotonated and can exit cells via PIN proteins. Polar cellular localisation of the carriers determines directionality of intercellular auxin flow |
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Term
| What controls organ position in plants? |
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Definition
| Polar auxin transport. Auxin in particular controls the plane of cell division and size of meristems, also timing |
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Term
| What controls the direction of auxin transport? |
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Definition
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Term
| How can we visualise PIN protein localisation? |
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Definition
| fuse it with GFP (green fluorescent protein) |
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Term
| What is the pattern of organ initiation at the shoot apical meristem called? What are some types? |
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Definition
Phyllotaxy
Alternate, opposite, whorled, spiral |
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Term
| What can cause changes in organ positioning through affecting PIN protein localisation? |
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Definition
| Gravitropism and phototropism (creates auxin buildups) |
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