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

Basic pattern of floral development A, B, C genes = transcription factors

The ABC model: model for floral organ identity determination Homeotic transformations Homeotic transformations –formation of a normal plant/animal body structure in place of another at an abnormal site – e.g., sepals forming in the 2 nd whorl ABC model: E. Coen and E. Meyerowitz 1991 ABC model: E. Coen and E. Meyerowitz 1991 ArabidopsisAntirrhinum ml

The ABC model: model for floral organ identity determination Sepal formation: needs class A genes Petal:A + B Stamen:B + C Carpel:C –Mutual inhibition of class A and class C function

Sexual reproduction 1.haploid gametogenesis in flowers: reproductive organs Female part = pistil (gynoecium) Stigma Style Ovary Ovules Male part : anthers Make pollen

(Wilson & Yang, 2004, Reproduction) Sexual reproduction 1. making haploid gametes in flowers Pollen = male, 2-3 cells Made in anther locules Archesporial cell Primary sporogenous cells Microspores Pollen mother cells Primary parietal cells 2 o parietal cells Endothecium Tapetum Middle cell layer meiosis

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 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 online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

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! One sperm fuses with egg to form zygote Other fuses with central cell to form 3n endosperm

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: 1 st division

Embryogenesis 1.Establishing polarity: 1 st division 2.Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue

Embryogenesis 1.Establishing polarity: 1 st division 2.Establishing radial patterning: periclinal divisions form layers that become dermal, ground & vascular tissue 3.Forming the root and shoot meristems

Embryogenesis 1.Establishing polarity: 1 st 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

Embryogenesis 1.Establishing polarity: 1 st 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 & pO 2

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 & pO 2 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

Plan B schedule- Spring 2013 DateTOPIC JAN14General Introduction 16plant structure I 18plant structure II 21plants and water I 23plants and water II 25mineral nutrition I 28mineral nutrition II 30solute transport I FEB1solute transport II 4Photosynthetic light reactions I 6Photosynthetic light reactions II 8Calvin cycle 11C4 and CAM 13Environmental effects 15Phloem transport I 18 Exam 1

20Phloem transport II 22Respiration I 25Respiration II 27Respiration III MAR1Lipid synthesis 4Spring Recess 6Spring Recess 8Spring Recess 11Biofuels 13Nutrient assimilation I 15Nutrient assimilation II 18Cell wall synthesis and growth I 20Cell wall synthesis and growth II 22Growth and development I 25Growth and development II 27Light regulation of growth I 29Easter APR1Easter

APR3Light regulation of growth II 5Growth regulators I 8Growth regulators II 10Growth regulators III 12Growth regulators IV 15Exam 2 17Elective 19Elective 22Elective 24Elective 26Elective 29Elective May1ElectiveLast Class! ???Final examination

Lab Schedule DateTOPIC Jan18General introduction, plant structure 25Water potential and transpiration Feb1Mineral nutrition 8Light reactions of photosynthesis 15CO 2 assimilation, C3 vs C4 and CAM 22Environmental effects on CO 2 assimilation Mar1Respiration 8Spring Recess 15Induction of nitrate reductase 22Growth and development I 29Easter Apr5Independent project 12Independent project 19Independent project 26 Independent project