Chapter 5 BOT3015L Regulation of Plant Growth by Plant HormonesTodayHormonesHormones in plantsAuxinDarwins’ (Charles and son) experimentEvidence for the role of auxin in apical dominanceEvidence for the role of auxin in adventitious root formationEvidence for the role of auxin in formation of fruit and structures of similar function (e.g. receptacle in strawberry)CytokininsPowerPoint PresentationCytokinin delays leaf senescence (ageing and reabsorption of aged organs)EthyleneExperimenting with plant response to ethylene commercial usesSlide 15Abscisic Acid (ABA)ABA induces stomatal closure a simplified diagramGibberellins Gibberellic acid (GA)Commercial use of GAWhat are the effects of GA on the growth of Brassica rapa?Slide 21Slide 22Slide 23How would you design an experiment?Aspects of good experimental designData collection and presentationTurn in…Slide 28Chapter 5BOT3015LRegulation of Plant Growth by Plant HormonesPresentation created by Danielle SherdanAll photos from Raven et al. Biology of Plants except when otherwise noted•The 5 main groups of plant hormones•Auxin•Cytokinins• Ethylene•Abscisic Acid•Gibberellins•Brassica rapa, a model plant species for experimentation•Design and begin group GA experimentsToday•The 5 main groups of plant hormones•Auxin•Cytokinins• Ethylene•Abscisic Acid•Gibberellins•Brassica rapa, a model plant species for experimentation•Design and begin group GA experimentsHormonesGreek horman = to stimulateSubstance or chemical that is transported and causes specific physiological effectsAlthough a topic throughout biology, in this course, we will use plants as examplesHormones in plants•Hormones can have effects on the cells that produce them and, after transport, at the target cells or tissues•Hormones can have inhibitory rather than stimulatory effects•5 main groups based on chemical structureAuxinProduction•Shoot tips•Developing seedsSome known actions•Establishment of polarity of root-shoot axis during embryogenesis•Cell elongation•Cell differentiation•Apical dominance•Lateral root formation and adventitious root formation•Fruit formationUnder normal conditions, shoot tips bend towards the lightWithout light on the tip, no bendingWhen not at tip, collar doesn’t prevent bendingConclusion: Light is sensed at the tip, but response not at tip New hypothesis: A substance or chemical is transportedAuxin later isolated from shoot tips and established to be involved in cell elongationDrawings depicting seedlings of Zea (Gramineae family)Darwins’ (Charles and son) experimentHigh auxin concentrationLow auxin concentrationDrawings depicting Coleus (Lamiaceae family)Evidence for the role of auxin in apical dominanceEvidence for the role of auxin in adventitious root formationWith synthetic auxin Without synthetic auxinSaintpaulia (Gesneriaceae family)Another example of misleading common nameThe African violet is not in the violet familyAdventitious roots growing from stem tissueEvidence for the role of auxin in formation of fruit and structures of similar function (e.g. receptacle in strawberry)Fragaria (Rosaceae family)Band of achenes removedWhat do you expect?Not shown: Auxin replacement restores normal fruit formation and can be used commercially to produce seedless fruitsAll achenes removedNormal conditionsWithout seed formation, fruits do not develop. Developing seeds are a source of auxin.However, too much auxin can kill the plant and thus synthetic auxins used commercially as herbicidesCytokininsProduction•Primarily root tipsSome known actions•Cell division (cytokinesis)•Tissue culture•Delay leaf senescenceIncreasing auxin concentrationIncreasing Cytokinin concentrationAuxin promotes root formationCytokinin promotes shoot formationLack of differentiation when both are presentCytokinin and auxin complexity of plant-hormone effects and interactionsCallus of Nicotiana (Solanaceae family)Cytokinin delays leaf senescence (ageing and reabsorption of aged organs)Transgenic UntreatedGenetic modification to increase cytokinin biosynthesisNicotiana (Solanaceae family)EthyleneProduction•In most tissues under stress, senescence, or ripeningSome known actions•Fruit ripening•Leaf and flower senescence •Leaf and fruit abscission (controlled separation of plant part from the main body)•Floral sex determination in monoecious species, promote femaleExperimenting with plant response to ethylenecommercial usesMutated ethylene receptorNormal ethylene receptor levelsBoth are 100 days after pickingLycopersicon (Solanaceae family)Experimenting with plant response to ethylenecommercial usesMutated ethylene receptorNormal ethylene receptor levels8 days after pollinationPetunia (Solanaceae family)Abscisic Acid (ABA)Production•Mature leaves, especially under stress•Roots, then transported to shootsSome known actions•Stress response•Stimulate stomatal closure•Inhibit premature germination of seeds•Embryogenesis•Seed dormancy maintenanceABA induces stomatal closurea simplified diagramSolutes (e.g. potassium and chloride ions) accumulate in guard cells causing water to accumulate in guard cells, making them turgidABA is one signal that causes guard cells to release solutes and thus release water, making them flaccid and closing the stoma (pore) between themGuard cell response to ABA is one topic of research in the Outlaw lab at FSUMore about guard cells and experiments with guard cells coming up in a couple of weeksGibberellinsGibberellic acid (GA)Production•In young, developing shoots and seedsSome known actions•Cell division•Cell elongation•Stimulate seed germination•Stimulate flowering•Stimulate fruit developmentCommercial use of GAThompson seedless grapes (Vitis (Vitaceae family)Without GA With GALarger fruits that are easier to clean are attractive in marketsWhat are the effects of GA on the growth of Brassica rapa?Why Brassica rapa?Image from wikipedia.org•The 5 main groups of plant hormones•Auxin•Cytokinins• Ethylene•Abscisic Acid•Gibberellins•Brassica rapa, a model plant species for experimentation•Design and begin group GA experimentsTodayWhat are the effects of GA on the growth of Brassica rapa?Why Brassica rapa?1. Many economically valuable plants in the (Brassicaceae family) Broccoli, cabbage, cauliflower, kale, radish, mustard, Canola oil2. Members of the Brassicaceae family have become model plant species. Some characteristics that are