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Plant Growth & Development 3 stages 1. Embryogenesis Fertilization to seed Plant Growth & Development 3 stages 1. Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult Plant Growth & Development 3 stages 1. Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition Plant Growth & Development 3 stages 1. Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition 3. Reproductive development Make flowers, can reproduce sexually Sexual reproduction 1. haploid gametogenesis in flowers: reproductive organs • Female part = pistil (gynoecium) • Stigma • Style • Ovary • Ovules Sexual reproduction 1. haploid gametogenesis in flowers: reproductive organs • Female part = pistil (gynoecium) • Stigma • Style • Ovary • Ovules • Male part : anthers • Make pollen Sexual reproduction 1. making haploid gametes in flowers • Pollen = male, 2-3 cells • Made in anther locules Archesporial cell Primary sporogenous cells Primary parietal cells Pollen mother 2o parietal cells cells Endothecium meiosis Tapetum Microspores Middle cell layer (Wilson & Yang, 2004, Reproduction) 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 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 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 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 Sexual reproduction 1. making haploid gametes in flowers • Pollen = male, contains 2-3 cells • Egg = female, made in ovaries 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 Sexual reproduction Megaspore mother cell → meiosis → 4 haploid megaspores • 3 die • Functional megaspore divides 3 x w/o cytokinesis http://www.biologie.uni-hamburg.de/bonline/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg 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 http://www.biologie.uni-hamburg.de/bonline/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg Sexual reproduction Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals • Egg, synergids & central cell are essential http://www.biologie.uni-hamburg.de/bonline/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg Sexual reproduction Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals • Egg, synergids & central cell are essential • In many spp antipodals degenerate http://www.biologie.uni-hamburg.de/bonline/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg Sexual reproduction 1. making haploid gametes in flowers 2. Pollen lands on stigma & germinates if good signals Sexual reproduction 1. making haploid gametes in flowers 2. Pollen lands on stigma & germinates if good signals • Forms pollen tube that grows through style to ovule 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 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 Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs! Sexual reproduction Pollen tube reaches micropyle & releases sperm nuclei into ovule Double fertilization occurs! One sperm fuses with egg to form zygote 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 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 Embryogenesis One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm Development starts immediately! Embryogenesis Development starts immediately! Controlled by genes, auxin & cytokinins Apical cell after first division becomes embryo, basal cell becomes suspensor Embryogenesis Development starts immediately! Controlled by genes, auxin & cytokinins Apical cell after first division becomes embryo, basal cell becomes suspensor Key events 1. Establishing polarity: starts @ 1st division Embryogenesis 1. Establishing polarity: starts @ 1st division 2. Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Embryogenesis 1. Establishing polarity: starts @ 1st division 2. Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue 3. Forming the root and shoot meristems 1. 2. 3. 4. Embryogenesis Establishing polarity: starts @ 1st division Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue Forming the root and shoot meristems Forming cotyledons & roots Embryogenesis 1. Establishing polarity: starts @ 1st division 2. Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue 3. Forming the root and shoot meristems 4. Forming cotyledons & roots Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems Embryogenesis End result is seed with embryo packaged inside protective coat Embryogenesis End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster) Embryogenesis End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster) In many dicots endosperm is absorbed as seed develops Embryogenesis End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster) In many dicots endosperm is absorbed as seed develops In many monocots endosperm is seedling food Embryogenesis Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems, roots & shoots Embryogenesis Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems, roots & shoots Later stages of seed development load nutrients and form protective coat Embryogenesis Later stages of seed development load nutrients and form protective coat Final stages involve desiccation (to 5% moisture content) & dormancy Embryogenesis Later stages of seed development involve loading nutrients and forming protective coat Final stages involve desiccation (to 5% moisture content) & dormancy -> Abscisic acid plays important role Embryogenesis Later stages of seed development load nutrients and form protective coat Final stages involve desiccation (to 5% moisture content) & dormancy -> Abscisic acid plays important role Coordinated with fruit ripening: fruit’s job is to protect & disperse seed Seed germination Coordinated with fruit ripening: fruit’s job is to protect & disperse seed Seeds remain dormant until sense appropriate conditions: some date palms germinated after 2000 years! Seed germination Seeds remain dormant until sense appropriate conditions: some date palms germinated after 2000 years! • Water Seed germination Seeds remain dormant until sense appropriate conditions: some Lotus germinated after 2000 years! • Water • Temperature: some seeds require vernalization = prolonged cold spell Seed germination Seeds remain dormant until sense appropriate conditions: some Lotus germinated after 2000 years! • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat Seed germination Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) Seed germination Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) • Many require light Seed germination Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) • Many require light: says that they will soon be able to photosynthesize Seed germination Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • May degrade hydrophobic seed coat • May disperse inhibitor (eg Abscisic acid) • Many require light: says that they will soon be able to photosynthesize: often small seeds with few reserves Seed germination Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • Many require light: says that they will soon be able to photosynthesize: often small seeds with few reserves • Some need acid treatment or scarification Seed germination Seeds remain dormant until sense appropriate conditions: • Water • Temperature: some seeds require vernalization = prolonged cold spell • Many require light: says that they will soon be able to photosynthesize: often small seeds with few reserves • Some need acid treatment or scarification • Passage through bird gut 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 Seed germination Seeds remain dormant until sense appropriate conditions: • Some need acid treatment or scarification • Passage through bird gut • Some need fire • Hormones can also trigger (or stop) germination Seed germination Seeds remain dormant until sense appropriate conditions: • Hormones can also trigger (or stop) 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. 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 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 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 Vegetative growth Once radicle has emerged, vegetative growth begins • Juvenile plants in light undergo photomorphogenesis • Initially live off reserves, but start making photosynthetic leaves Vegetative growth Once radicle has emerged, vegetative growth begins • Juvenile plants in light undergo photomorphogenesis • Initially live off reserves, but start making photosynthetic leaves • Roots grow down seeking water & nutrients reproductive phase Eventually switch to reproductive phase & start flowering • Are now adults! reproductive phase Eventually switch to reproductive phase & start flowering • Are now adults! • Time needed varies from days to years 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
