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phystohormones
- class; auxin, giberellins, cutokinins
- specific, abscisic acid
- molecules, ethylene gas
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auxin?
acidic acid chain, one aromatic ring,
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auxin location?
throughout plant, highest conc in meri and growing tissue, synthesised in embryo and meristems
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auxin funstion?
cell elongation, root initiation, roles in other random developmental shit.
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sythetic auxin include?
- 2,4 - d (herbicide) stimulates growth elongation and its high energy requirement eventually kills plant
- and Napthalene(NAA) induces root growth and prevents fruit from abscission
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Gibberellins?
- all have same 3 carbon ring skeleton
- role in flower and fruit development
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Gibberellins location?
synth in and found in; developing seed and fruit, young leaves and shoot apex, root apex
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Gibberellins function?
stem elongation(via cell wall expansion), break dormancy of buds and seeds, young plants elongation of cells same number of leaves and roots, if stem fully developed then nothing rly
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plant dormancy?
GA cues plant to release from dormancy,,,bud or seed
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GA stimulates?
synthesis of a-amylase in aleurone layer of seed,break down starch in endosperm,,which gets used for energy by seedling
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Parthenocarpy?
- seedless fruit: spray flowers with GA at right time
- interferes with seed development
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GA interarts with auxin to?
control sex expression in monoecious plants
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synoecious?
perfect single flower with male and female organs
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monoecious ?
one sex per flower, multiple flowers per plant...can be gyno and andro if exposed to certain hormones such as auxin or GA
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gynoecious?
all female flowers
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androecious?
all male flowers
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dioecious?
one sex perplant no exceptions
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cytokinins?
derivative of adenin, lots of nitrogen
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CK location?
synth in root, transport in xlem, high conc in immature seeds and developing fruit, delays senescence (aging)
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CK function?
stimulate cell division, active in most aspect of grwth and dvlpmnt
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abscisic acid (ABA)?
specific molecule no variant,
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ABA location?
mature leaves, synth in cytoplasm of mesophyll cells(cntr of leaf)
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ABA function?
storage protein synth during seed dvlpmnt,prevents germination,,,dormancy is a balance of ABA + GA, modulates water stress-close stomata to prevent water loss..
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ABA factoid>
causes influx of Ca into cells, high conc in human brain.. involved in intracellular pathways it a conserved mech of evol
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ethylene?
found throughout plant,especially in epidermis,seed coat,and senesing and ripening tissue,,,,synth in response to stress>including excess auxin
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ethylene function?
inhibits auxin synthesis,,inhibits elongation,promotes radial growth(thinkness),primary role is to promote flowering and fruit ripening
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ethylene facts..
autocatalytic(positive feedback), control sex expression in monoecious plants>spraying w ethylene makes F flowers
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brassinosteroids?
4 c ring steroid hormon, found throughout
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Bsteroids function?
stimulate shoot elongation, ethylene production>which inhibits root grwth and dvlpmnt
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polyamines
protein stability, membrane permeability
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jasmonates
seed germination, defense proteins (insect and disease resistant)
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meristems undergo
mitosis, growth, differentiation
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cell division is stimulated by
auxins and cytokinins
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celldivision
cell proliferation occurs w auxins and CK
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auxin and CK promote?
accumulation of cyclin D reuired to activate CDK , promotes transiton from G-synth
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DEVELOPMENT (auxin and CK)
absence of either auxin or CK arrests cell in G1 or G2, remove either to create barrier
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Auxin stimulates?
increase cell size, signal on tip sends down to dark side cells to grow,,,bend to light.
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acid growth hyp
auxin increase the sensibility of cell wall, it decreases ph so atp actively transports H out of cell... (active expansion
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agh cont
indirect action between auxin and atpase..auxin receptors intiate a signal transduction mech
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agh on applies to
- initial rapid growth (first hour)
- need to add synthesis of of new wall units to avoid stretching to thin, small auxin upregulated RNAs(saurs gene),aux/iaa genes
- (10-60 minutes after auxin added)
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transport of auxin
shoots mostly, basipetally (apex to base,,,minimal acropetal) transports both ways.. not gravity induced...
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chemiosmotic hyp.
ph gradient drives iaa uptake, polar iaa efflux ... gradient
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auxin plays a role in
apical dominance...high conc from apical bud dormants lateral buds...CK release buds from dormancy..
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vascular differntiation regulated by
auxin and CK...
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seed development
fert,embry dvlpmnt/endosperm formation, auxin and GA>cell enlargement/build nutrient reserve, maturation (aba) prep for dormancy.
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aba prevents
seed germination while still in fruit
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seed germination
- imbibition
- (water uptake), embryo elongation (iaa) ga induced A-amylase (mobilize nut reserves), seed grows
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imbibition
taking up water.... seed dehydrate be4 formancy, take up water to grow.. some need to break coat inorder to absorb...
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embry elongation
(need iaa) supplied from stores untill embry can produce its own
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mobilization and nutrients.
GA induced A-amylase, embry intiates seq of events
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GA causes
internodal elngation in stems, and it causes bolting...growth of stems as opposed to rosette just leaves...
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GA is
threshold dependent...in stem growth its triggered by photoperiod and low temp
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ethylene stunts
plant growth
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root development
auxin very low >root growth....mid inhibits root growth...higher> promotes initaiation of secondary roots...
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shoot:root
- CK>auxin=shoot
- CKCK=auxin=callus
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elongation vs dvsion and elongation
auxin only elong...auxin and CK divide and elongate
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ethylene promotes
senescences of leaves and fruits
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abcission layer
when scenescence/stress auxin leaves leaf this causes abcission layer...
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flowers
auxin and ethylene female...GA male..
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parthenocarpy
auxin or GA depends on species
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