Plant Growth & Development3 stages1. Embryogenesis

Fertilization to seed2. Vegetative growth

Juvenile stageGermination to adult"phase change" marks transition

3. Reproductive developmentMake flowers, can reproduce sexually

Basic pattern offloral development

http://en.wikipedia.org/wiki/File:Flower_poster_2.jpg

A, B, C genes = transcription factors

The ABC model: model forfloral organ identity determination

Homeotic transformationsHomeotic transformations

– formation of a normal plant/animal body structure in place of another at an abnormal site

– e.g., sepals forming in the 2nd whorl

ABC model: E. Coen and E. ABC model: E. Coen and E. Meyerowitz 1991Meyerowitz 1991

Arabidopsis Antirrhinum

http://biology.kenyon.edu/courses/biol114/Chap13/Chapter_12C.html

The ABC model: model forfloral organ identity determination

Sepal formation: needs class A genes

Petal: A + BStamen: B + CCarpel: C

–Mutual inhibition of class A and class C function

http://www.its.caltech.edu/~plantlab/html/research.html

Sexual reproduction1. haploid gametogenesis in flowers: reproductive organs•Female part = pistil (gynoecium)•Stigma•Style•Ovary •Ovules

•Male part : anthers•Make pollen

(Wilson & Yang, 2004, Reproduction)

Sexual reproduction1. making haploid gametes in flowers• Pollen = male, 2-3 cells• Made in anther locules

Archesporial cell

Primarysporogenous

cells

Microspores

Pollen mothercells

Primaryparietal

cells

2o parietal cellsEndothecium

Tapetum Middle cell layermeiosis

Sexual reproduction1. 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 reproduction1. making haploid gametes in flowers• Pollen = male, contains 2-3 cells• Egg = female, made in ovaries

Sexual reproductionMegaspore 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/b-online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

Sexual reproductionPollen lands on stigma & germinates if good signals• Forms pollen tube that grows

through style to ovule• Germ cell divides to form sperm

nucleiPollen tube reaches micropyle& releases sperm nuclei into ovule

Sexual reproductionPollen tube reaches micropyle& releases sperm nuclei into ovuleDouble fertilization occurs!One sperm fuses with egg to form zygoteOther fuses with central cell to form 3n endosperm

EmbryogenesisOne sperm fuses with egg to form zygoteOther fuses with central cell to form 3n endospermDevelopment starts immediately!

EmbryogenesisDevelopment starts immediately! Controlled by genes,

auxin & cytokininsApical cell after first division becomes embryo, basal cell

becomes suspensor

EmbryogenesisDevelopment starts immediately! Controlled by genes,

auxin & cytokininsApical cell after first division becomes embryo, basal cell

becomes suspensorKey events1. Establishing polarity: starts @ 1st division

Embryogenesis1. Establishing polarity: starts @ 1st division2. Establishing radial patterning: periclinal divisions form

layers that become dermal, ground & vascular tissue

Embryogenesis1. Establishing polarity: starts @ 1st division2. Establishing radial patterning: periclinal divisions form

layers that become dermal, ground & vascular tissue3. Forming the root and shoot meristems

Embryogenesis1. Establishing polarity: starts @ 1st division2. Establishing radial patterning: periclinal divisions form

layers that become dermal, ground & vascular tissue3. Forming the root and shoot meristems4. Forming cotyledons & roots

Embryogenesis1. Establishing polarity: starts @ 1st division2. Establishing radial patterning: periclinal divisions form

layers that become dermal, ground & vascular tissue3. Forming the root and shoot meristems4. Forming cotyledons & roots Body plan is formed during embryogenesis: seedling that

germinates is a juvenile plant with root and apical meristems

EmbryogenesisEnd result is seed with embryo packaged inside protective

coat

EmbryogenesisEnd result is seed with embryo packaged inside protective

coatEndosperm feeds developing embryo (3n grows faster)

EmbryogenesisEnd result is seed with embryo packaged inside protective

coatEndosperm feeds developing embryo (3n grows faster)In many dicots endosperm is absorbed as seed develops

EmbryogenesisEnd result is seed with embryo packaged inside protective

coatEndosperm feeds developing embryo (3n grows faster)In many dicots endosperm is absorbed as seed developsIn many monocots endosperm is seedling food

EmbryogenesisBody plan is formed during embryogenesis: seedling that

germinates is a juvenile plant with root and apical meristems, roots & shoots

EmbryogenesisBody 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

EmbryogenesisLater stages of seed development load nutrients and form

protective coatFinal stages involve desiccation (to 5% moisture content)

& dormancy

EmbryogenesisLater stages of seed development involve loading nutrients

and forming protective coatFinal stages involve desiccation (to 5% moisture content)

& dormancy -> Abscisic acid plays important role

EmbryogenesisLater stages of seed development load nutrients and form

protective coatFinal stages involve desiccation (to 5% moisture content)

& dormancy -> Abscisic acid plays important roleCoordinated with fruit ripening: fruit’s job is to protect &

disperse seed

Seed germinationCoordinated with fruit ripening: fruit’s job is to protect &

disperse seedSeeds remain dormant until sense appropriate conditions:some date palms germinated after 2000 years!

Seed germinationSeeds remain dormant until sense appropriate conditions:some date palms germinated after 2000 years!• Water

Seed germinationSeeds remain dormant until sense appropriate conditions:some Lotus germinated after 2000 years!• Water• Temperature: some seeds require vernalization =

prolonged cold spell

Seed germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds 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 germinationSeeds remain dormant until sense appropriate conditions:• Hormones can also trigger (or stop) germinationGermination is a two step process• Imbibition is purely physical: seed swells as it absorbs

water until testa pops. Even dead seeds do it.

Seed germinationGermination 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 germinationGermination 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 germinationGermination 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 growthOnce radicle has emerged, vegetative growth begins• Juvenile plants in light undergo photomorphogenesis• Initially live off reserves, but start

making photosynthetic leaves

Vegetative growthOnce 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 phaseEventually switch to reproductive phase & start flowering• Are now adults!

reproductive phaseEventually switch to reproductive phase & start flowering• Are now adults!• Time needed varies from days to years

reproductive phaseEventually 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 2013Date TOPIC

JAN 14 General Introduction16 plant structure I18 plant structure II 21 plants and water I23 plants and water II25 mineral nutrition I28 mineral nutrition II30 solute transport I

FEB 1 solute transport II4 Photosynthetic light reactions I6 Photosynthetic light reactions II8 Calvin cycle11 C4 and CAM13 Environmental effects15 Phloem transport I18 Exam 1

20 Phloem transport II22 Respiration I25 Respiration II27 Respiration III

MAR 1 Lipid synthesis4 Spring Recess6 Spring Recess8 Spring Recess11 Biofuels13 Nutrient assimilation I15 Nutrient assimilation II18 Cell wall synthesis and growth I20 Cell wall synthesis and growth II22 Growth and development I25 Growth and development II27 Light regulation of growth I29 Easter

APR 1 Easter

APR 3 Light regulation of growth II5 Growth regulators I8 Growth regulators II10 Growth regulators III12 Growth regulators IV15 Exam 217 Elective19 Elective22 Elective24 Elective26 Elective29 Elective

May 1 Elective Last Class!

??? Final examination

Lab ScheduleDate TOPICJan 18 General introduction, plant structure

25 Water potential and transpirationFeb 1 Mineral nutrition

8 Light reactions of photosynthesis15 CO2 assimilation, C3 vs C4 and CAM22 Environmental effects on CO2 assimilation

Mar 1 Respiration 8 Spring Recess15 Induction of nitrate reductase22 Growth and development I29 Easter

Apr 5 Independent project12 Independent project19 Independent project

26 Independent project