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Plant Growth & Development
3 stages Embryogenesis Fertilization to seed
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Plant Growth & Development
3 stages Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult
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Plant Growth & Development
3 stages Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition
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Plant Growth & Development
3 stages Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition 3. Reproductive development Make flowers, can reproduce sexually
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Sexual reproduction haploid gametogenesis in flowers: reproductive organs Female part = pistil (gynoecium) Stigma Style Ovary Ovules
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Sexual reproduction haploid gametogenesis in flowers: reproductive organs Female part = pistil (gynoecium) Stigma Style Ovary Ovules Male part : anthers Make pollen
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Primary sporogenous cells Primary parietal cells
Sexual reproduction 1. making haploid gametes in flowers Pollen = male, 2-3 cells Made in anther locules (Wilson & Yang, 2004, Reproduction) Archesporial cell Primary sporogenous cells Microspores Pollen mother cells Primary parietal cells 2o parietal cells Endothecium Tapetum Middle cell layer meiosis
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Sexual reproduction 1. making haploid gametes in flowers Pollen = male, contains 2-3 cells Made in anthers Microspores divide to form vegetative cell and germ cell
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Sexual reproduction 1. making haploid gametes in flowers Pollen = male, contains 2-3 cells Made in anthers Microspores divide to form vegetative cell and germ cell Germ cell divides to form 2 sperm cells, but often not until it germinates
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Sexual reproduction 1. making haploid gametes in flowers Pollen = male, contains 2-3 cells Made in anthers Microspores divide to form vegetative cell and germ cell Germ cell divides to form 2 sperm cells, but often not until it germinates Pollen grains dehydrate and are coated
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Sexual reproduction 1. making haploid gametes in flowers Pollen = male, contains 2-3 cells Made in anthers Microspores divide to form vegetative cell and germ cell Germ cell divides to form 2 sperm cells, but often not until it germinates Pollen grains dehydrate and are coated Are released, reach stigma, then germinate
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Sexual reproduction 1. making haploid gametes in flowers Pollen = male, contains 2-3 cells Egg = female, made in ovaries
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Sexual reproduction 1. making haploid gametes in flowers Pollen = male, contains 2-3 cells Egg = female, made in ovaries Megaspore mother cell → meiosis → 4 haploid megaspores
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Megaspore mother cell → meiosis → 4 haploid megaspores 3 die
Sexual reproduction Megaspore mother cell → meiosis → 4 haploid megaspores 3 die Functional megaspore divides 3 x w/o cytokinesis
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Megaspore mother cell → meiosis → 4 haploid megaspores 3 die
Sexual reproduction Megaspore mother cell → meiosis → 4 haploid megaspores 3 die Functional megaspore divides 3 x w/o cytokinesis Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals
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Egg, synergids & central cell are essential
Sexual reproduction Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals Egg, synergids & central cell are essential
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Egg, synergids & central cell are essential
Sexual reproduction Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals Egg, synergids & central cell are essential In many spp antipodals degenerate
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Sexual reproduction making haploid gametes in flowers Pollen lands on stigma & germinates if good signals
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Sexual reproduction making haploid gametes in flowers Pollen lands on stigma & germinates if good signals Forms pollen tube that grows through style to ovule
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Sexual reproduction Pollen lands on stigma & germinates if good signals Forms pollen tube that grows through style to ovule Germ cell divides to form sperm nuclei
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Sexual reproduction Pollen lands on stigma & germinates if good signals Forms pollen tube that grows through style to ovule Germ cell divides to form sperm nuclei Pollen tube reaches micropyle & releases sperm nuclei into ovule
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Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs!
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Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs! One sperm fuses with egg to form zygote
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Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs! One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm
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Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs! One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm Synergids play key role in releasing & guiding sperm cells
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Embryogenesis One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm Development starts immediately!
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Embryogenesis Development starts immediately! Controlled by genes, auxin & cytokinins Apical cell after first division becomes embryo, basal cell becomes suspensor
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Embryogenesis Development starts immediately! Controlled by genes, auxin & cytokinins Apical cell after first division becomes embryo, basal cell becomes suspensor Key events Establishing polarity: 1st division
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Embryogenesis Establishing polarity: 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue
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Embryogenesis Establishing polarity: 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems
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Embryogenesis Establishing polarity: 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems Forming cotyledons & roots
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Embryogenesis Establishing polarity: 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems Forming cotyledons & roots Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems
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Embryogenesis End result is seed with embryo packaged inside protective coat
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Seed germination Seeds remain dormant until sense appropriate conditions: Water Temperature Many require light Some need acid treatment or scarification Passage through bird gut Some need fire
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Seed germination Germination is a two step process Imbibition is purely physical: seed swells as it absorbs water until testa pops. Even dead seeds do it. Next embryo must start metabolism and cell elongation This part is sensitive to the environment, esp T & pO2 Once radicle has emerged, vegetative growth begins
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Vegetative growth Once radicle has emerged, vegetative growth begins Juvenile plants in light undergo photomorphogenesis
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Vegetative growth Once radicle has emerged, vegetative growth begins Juvenile plants in light undergo photomorphogenesis Juvenile plants in dark undergo skotomorphogenesis Seek light: elongate hypocotyl, don’t unfold cotyledons
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Vegetative growth Once radicle has emerged, vegetative growth begins Juvenile plants in light undergo photomorphogenesis Expand cotyledons, start making leaves & photosynthetic apparatus
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Vegetative growth Once radicle has emerged, vegetative growth begins Juvenile plants in light undergo photomorphogenesis Expand cotyledons, start making leaves & photosynthetic apparatus Initially live off reserves, but soon do net photosynthesis
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Vegetative growth Once radicle has emerged, vegetative growth begins Initially live off reserves, but soon do net photosynthesis Add new SAM in response to auxin gradients Add new branches from axillary buds lower down stem if apical dominance wanes
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Vegetative growth Once radicle has emerged, vegetative growth begins Add new SAM in response to auxin gradients Add new branches from axillary buds lower down stem if apical dominance wanes Roots grow down seeking water & nutrients
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Vegetative growth Once radicle has emerged, vegetative growth begins Add new SAM in response to auxin gradients Roots grow down seeking water & nutrients 1Ëš (taproot) anchors plant 2Ëš roots absorb nutrients
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Vegetative growth Once radicle has emerged, vegetative growth begins Add new SAM in response to auxin gradients Roots grow down seeking water & nutrients 1Ëš (taproot) anchors plant 2Ëš roots absorb nutrients Continue to add cells by RAM
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Vegetative growth Roots grow down seeking water & nutrients Continue to add cells by RAM Form lateral roots in maturation zone in response to nutrients & auxin/cytokinin
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reproductive phase Eventually switch to reproductive phase & start flowering Are now adults!
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reproductive phase Eventually switch to reproductive phase & start flowering Are now adults! Triggered by FT protein: moves from leaves to shoot apex in phloem to induce flowering!
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Transition to Flowering
Adults are competent to flower, but need correct signals Very complex process! Can be affected by: Daylength T (esp Cold) Water stress Nutrition Hormones Age
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reproductive phase Are now adults! Very complex process! Time needed varies from days to years
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reproductive phase Eventually switch to reproductive phase & start flowering Are now adults! Time needed varies from days to years. Shoot apical meristem now starts making new organ: flowers, with many new structures & cell types
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Senescence Shoot apical meristem now starts making new organ: flowers, with many new structures & cell types Eventually petals, etc senesce = genetically programmed cell death: controlled by specific genes
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Senescence Eventually petals, etc senesce = genetically programmed cell death: controlled by specific genes Also seen in many other cases: deciduous leaves in fall, annual plants, older trees
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Senescence Induce specific senescence-associated genes ; eg DNAses, proteases, lipases Also seen during xylem formation: when cell wall is complete cell kills itself
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Senescence Also seen during xylem formation: when cell wall is complete cell kills itself Also seen as wound response: hypersensitive response Cells surrounding the wound kill themselves
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Senescence Also seen during xylem formation: when cell wall is complete cell kills itself Also seen as wound response: hypersensitive response Cells surrounding the wound kill themselves Some mutants do this w/o wound -> is controlled by genes!
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Light regulation of Plant Development
Plants use light as food and information Use information to control development
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Light regulation of Plant Development
Plants use light as food and information Use information to control development germination
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Light regulation of Plant Development
Plants use light as food and information Use information to control development Germination Photomorphogenesis vs skotomorphogenesis
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Light regulation of Plant Development
Plants use light as food and information Use information to control development Germination Photomorphogenesis vs skotomorphogenesis Sun/shade & shade avoidance
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Light regulation of Plant Development
Germination Morphogenesis Sun/shade & shade avoidance Flowering
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Light regulation of Plant Development
Germination Morphogenesis Sun/shade & shade avoidance Flowering Senescence
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Light regulation of growth
Plants sense Light quantity
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Light regulation of growth
Plants sense Light quantity Light quality (colors)
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Light regulation of growth
Plants sense Light quantity Light quality (colors) Light duration
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Light regulation of growth
Plants sense Light quantity Light quality (colors) Light duration Direction it comes from
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Light regulation of growth
Plants sense Light quantity Light quality (colors) Light duration Direction it comes from Have photoreceptors that sense specific wavelengths
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Light regulation of growth
Early work: Darwin showed that phototropism is controlled by blue light
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Light regulation of Plant Development
Early work: Darwins : phototropism is controlled by blue light Duration = photoperiodism (Garner and Allard,1920) Maryland Mammoth tobacco flowers in the S but not in N
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Light regulation of Plant Development
Early work: Darwins : phototropism is controlled by blue light Duration = photoperiodism (Garner and Allard,1920) Maryland Mammoth tobacco flowers in the S but not in N = short-day plant (SDP)
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Light regulation of Plant Development
Duration = photoperiodism (Garner and Allard,1920) Maryland Mammoth tobacco flowers in the S but not in N = short-day plant (SDP) Measures night! 30" flashes during night stop flowers
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Light regulation of growth
Duration = photoperiodism (Garner and Allard,1920) Maryland Mammoth tobacco flowers in the S but not in N = short-day plant (SDP) Measures night! 30" flashes during night stop flowers LDP plants such as Arabidopsis need long days to flower
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Light regulation of growth
Duration = photoperiodism (Garner and Allard,1920) Maryland Mammoth tobacco flowers in the S but not in N = short-day plant (SDP) Measures night! 30" flashes during night stop flowers LDP plants such as Arabidopsis need long days to flower SDP flower in fall, LDP flower in spring, neutral flower when ready
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Light regulation of growth
Measures night! 30" flashes during night stop flowers LDP plants such as Arabidopsis need long days to flower SDP flower in fall, LDP flower in spring, neutral flower when ready Next : color matters! Red light works best for flowering
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Light regulation of growth
Next : color matters! Red light (666 nm)works best for flowering & for germination of many seeds!
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Phytochrome Next : color matters! Red light (666 nm)works best for flowering & for germination of many seeds! But, Darwin showed blue works best for phototropism!
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Phytochrome Next : color matters! Red light (666 nm)works best for flowering & for germination of many seeds! But, Darwin showed blue works best for phototropism! Different photoreceptor!
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Phytochrome But, Darwin showed blue works best for phototropism! Different photoreceptor! Red light (666 nm) promotes germination Far red light (>700 nm) blocks germination
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Phytochrome But, Darwin showed blue works best for phototropism! Different photoreceptor! Red light (666 nm) promotes germination Far red light (>700 nm) blocks germination
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Phytochrome Red light (666 nm) promotes germination Far red light (>700 nm) blocks germination After alternate R/FR flashes last flash decides outcome
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Phytochrome Red light (666 nm) promotes germination Far red light (>700 nm) blocks germination After alternate R/FR flashes last flash decides outcome Seeds don't want to germinate in the shade!
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Phytochrome Red light (666 nm) promotes germination Far red light (>700 nm) blocks germination After alternate R/FR color of final flash decides outcome Seeds don't want to germinate in the shade! Pigment is photoreversible
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Phytochrome Red light (666 nm) promotes germination Far red light (730 nm) blocks germination After alternate R/FR color of final flash decides outcome Pigment is photoreversible! -> helped purify it! Looked for pigment that absorbs first at 666 nm, then 730
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Phytochrome Red light (666 nm) promotes germination Far red light (730 nm) blocks germination After alternate R/FR color of final flash decides outcome Pigment is photoreversible! -> helped purify it! Looked for pigment that absorbs first at 666 nm, then 730
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Phytochrome Red light (666 nm) promotes germination Far red light (730 nm) blocks germination After alternate R/FR color of final flash decides outcome Pigment is photoreversible! -> helped purify it! Looked for pigment that absorbs first at 666 nm, then 730 Made as inactive cytoplasmic Pr that absorbs at 666 nm
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Phytochrome Made as inactive cytoplasmic Pr that absorbs at 666 nm or in blue Converts to active Pfr that absorbs far red (730nm)
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