plant regulation
DESCRIPTION
Plant Regulation. Chapter 39. Plant growth. Plants respond to environment Growth response to abiotic factors Water, wind & light. Plant responses. Light Gravity Touch Water Temperature. Plant hormones. Internal signal (developmental) Environmental signal Chemical binds receptor - PowerPoint PPT PresentationTRANSCRIPT
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Plant Regulation
Chapter 39
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Plant growth
Plants respond to environmentGrowth response to abiotic factorsWater, wind & light
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Plant responses
LightGravityTouchWater Temperature
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Plant hormones
Internal signal (developmental)Environmental signalChemical binds receptorPhysiological responseDevelopmental responseReception-transduction-responseRegulate growth & developmentNew protein or activation of protein
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Signal transduction pathway
CYTOPLASMCELLWALL
Plasma membrane
second messengers
Relay proteins andReceptor
Hormone orenvironmentalstimulus
Activationof cellularresponses
Transduction ResponseReception1 2 3
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Potato plant de-etiolation (greening)
(a) Before exposure to light (b) After a week’s exposureto natural daylight
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Potato response
Reception
CYTOPLASM
Plasmamembrane
Phytochromeactivatedby light
Cellwall
Light
1 Transduction
cGMP
Secondmessengerproduced
Proteinkinase 1
2
Ca2+ channelopened
Ca2+
De-etiolation(greening)responseproteins
Translation
Transcription
Transcriptionfactor 2
NUCLEUSTranscriptionfactor 1
Response3
P
P
Proteinkinase 2
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Light response
Photomorphogenesis:Nondirectional light-triggered developmentChange in formFlower formationPhototropisms:Directional developmentTrope (turn)
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Plant hormones
AuxinCytokininsGibberellinsBrassinosteriodsEthyleneAbscisic acid
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Auxin
First plant hormone(IAA) Indoleacetic acidFound in apical meristems of shootsPromotes activity of vascular cambium Promotes lateral root growthFound in pollen, fruit development
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Auxins
Plasticity (soften) of plantElongation of plantAuxin moves from light exposed sideTo shady sideBends towards light
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Auxins
Synthetic auxinsPrevent apples from dropping earlyBerries on hollySeedless tomatoes Control weeds
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Cytokinins
Similar to adenine (purines)Cell division & differentiationFound in root apical meristems Transported through plantLateral buds into branchesInhibit lateral roots (auxin promotes)
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Cytokinins
Remove terminal bud Plant becomes bushierPromotes lateral buds into branchesAuxin on cut surface Inhibits lateral buds
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Cytokinins
Applied to cut leaves prevent agingFlorists spray on fresh cut flowersCrown gallTumor growth on treesBacteria causes increased production of auxin & cytokinins
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Gibberellins
Stem elongationEnhances if auxin presentFound in apical portions of stems & rootsApply to dwarf plants restores normal growth
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Gibberellins
Stimulate enzymes that utilize food during germinationHastens germinationFruit developmentHelps space grape leaves (internodes)Fruits have more space to grow
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Brassinosteriods
Similar in structure to testosterone, estradiol, cortisolElongation & cell divisionBending of stemsReproductive developmentDelays senescence
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Abscisic Acid
In mature green leaves, fruit & root capsFormation of winter budsInduce seed dormancyControls stomata open/close
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Ethylene
GasSuppresses stem & root elongationHastens fruit ripening Response to stressLeaf abscissionProgrammed cell death
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Ethylene
Mechanical stress on stem tip.Triple response Enables a seedling to avoid an obstacle.
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Ethylene
Commercially sprayed on green tomatoes Hastens ripening
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Light response
Certain wavelengths of light Initiate biological changePhytochrome: Pigment containing proteinPr (inactive form)
Pfr(active form)
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Light response
Inter-convertible formsPr absorbs red light (660nm)Converts to the active form Pfr
Pfr absorbs far red light (730 nm)Converts to the inactive form Pr
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Light response
Acts as switching mechanism Controls various light-induced eventsPhytochrome exposed to red light Pr is converted to Pfr
Triggering germinationFar-red light inhibits germination
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Light response
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Light response
Determine plant spacing Pfr plant grows tallPr plant branches
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Circadian clocks
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GravitropismResponse of plant to gravitational pullShoot negative gravitropic responseRoots positive gravitropic response
Gravity response
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Gravity response
Amyloplasts:Starch containing organellesMaybe involved in sensing gravityStem located in the endoplasmRoot located in the root capRoot cap is involved in sensing gravity
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Touch response
ThigmotropismDirectional growth responseDirection of touch Object, animal, windThigmonasticResponds in one directionDespite where the contact is
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Touch response
Tendril touches an object
Uneven growth
Wraps around the object
Fly trap
Touch hairs, closes (0.3 sec)
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Turgor Movement
Touch induces change in turgorCells collapseCauses leaf movementPulvini:Multicellular swellings Located base of leaf or leaflet
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Turgor movement
Environmental stimuli Rapid loss of K+ out of half the pulvini cellsWater followsCauses cells to be flaccidLeaves fold in Reverses in approx 15-30 minutes
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media\39_26MimosaLeaf_SV.mpg
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Dormancy
Survive environment extremesSignals that initiate or terminate dormancyTemperate regions dormancy occurs during winter (day-length)Dry climates dormancy comes in summer (rainfall)
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Plant defense
First defense Dermal tissue systemCutin, suberinBark, thorns, trichomes
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Plant defense
PoisonsCyanide-containing compoundsStops electron-transport Cassava (African food)Secondary metabolitesAlkaloids (caffeine, nicotine, cocaine, and morphine)
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Plant defense
Soy products produce PhytoestrogensSimilar in structure to estrogenDecreased prostate cancer in Asian menHelp minimize menopausal symptoms
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Plant defense
Pacific Yew produces TaxolFights cancer especially breast cancerCinchona tree bark Quinine Anti-malaria drug
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Plant defenses
Toxic when metabolized by herbivore
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Plant defense
Allelopathy:When a chemical secreted by roots Inhibits growth of other plantsBlack walnut trees
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Plant defense
Plant is injuredCell death at locationPrevents further spread of pathogenH2O2 & NO can be produced
Can cause harm to invaderChemicals released to warn other plants of an invasion
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Wasps