Plant Growth & Development 3 stages Embryogenesis Fertilization to seed

Plant Growth & Development 3 stages Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult

Plant Growth & Development 3 stages Embryogenesis Fertilization to seed 2. Vegetative growth Juvenile stage Germination to adult "phase change" marks transition

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

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

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

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

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

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 http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

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 http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

Egg, synergids & central cell are essential Sexual reproduction Cellularization forms egg, binucleate central cell, 2 synergids & 3 antipodals Egg, synergids & central cell are essential http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

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 http://www.biologie.uni-hamburg.de/b-online/library/webb/BOT201/Angiosperm/MagnoliophytaLab99/OvuleForm700.jpg

Sexual reproduction making haploid gametes in flowers Pollen lands on stigma & germinates if good signals

Sexual reproduction making haploid gametes in flowers 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 Cell division = growth Determination = what cell can become Differentiation = cells become specific types

Embryogenesis Cell division = growth Determination = what cell can become Differentiation = cells become specific types Pattern formation: developing specific structures in specific locations

Embryogenesis Cell division = growth Determination = what cell can become Differentiation = cells become specific types Pattern formation Morphogenesis: organization into tissues & organs

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 Body plan is formed during embryogenesis: seedling that germinates is a juvenile plant with root and apical meristems

Seeds Seeds are unique feature of plants

Seeds Seeds are unique feature of plants Plant dispersal units

Seeds Seeds are unique feature of plants Plant dispersal units Must survive unfavorable conditions until they reach suitable place (and time) to start next generation

Seeds Seeds are unique feature of plants Plant dispersal units Must survive unfavorable conditions until they reach suitable place (and time) to start next generation Are dormant

Seeds Seeds are unique feature of plants Plant dispersal units Must survive unfavorable conditions until they reach suitable place (and time) to start next generation Are dormant; dehydration is key

Seeds Seeds are unique feature of plants Plant dispersal units Must survive unfavorable conditions until they reach suitable place (and time) to start next generation Are dormant; dehydration is key Germinate when conditions are right

Seeds Germinate when conditions are right Need way to sense conditions while dormant

Seeds Germinate when conditions are right Need way to sense conditions while dormant Need reserves to nourish seedling until it is established

Seeds (Usually) required for fruit development!

Seeds (Usually) required for fruit development! Role of fruit is to aid seed dispersal!

Seed Development (Usually) required for fruit development! Role of fruit is to aid seed dispersal! Unfertilized flowers don’t develop fruit

Seed Development (Usually) required for fruit development! Role of fruit is to aid seed dispersal! Unfertilized flowers don’t develop fruits The growth regulators GA, auxin or cytokinin can all induce parthenocarpy

Seed Development (Usually) required for fruit development! Role of fruit is to aid seed dispersal! Unfertilized flowers don’t develop fruits The growth regulators GA, auxin or cytokinin can all induce parthenocarpy GA + auxin or GA + cytokinin work best

Seed Development (Usually) required for fruit development! Role of fruit is to aid seed dispersal! Unfertilized flowers don’t develop fruits The growth regulators GA, auxin or cytokinin can all induce parthenocarpy GA + auxin or GA + cytokinin work best Hormones from embryo stimulate fruit development

Seed Development Hormones from embryo stimulate fruit development Other floral organs make inhibitor that blocks fruit development until they abscise

Seed Development Hormones from embryo stimulate fruit development Other floral organs make inhibitor that blocks fruit development until they abscise Divide seed development into three phases of ± equal time

Seed Development Divide seed development into three phases of ± equal time Morphogenesis

Seed Development Divide seed development into three phases of ± equal time Morphogenesis Maturation

Seed Development Divide seed development into three phases of ± equal time Morphogenesis Maturation Dehydration and dormancy

Seed Development End result is seed with embryo packaged inside protective coat

Seed Development End result is seed with embryo packaged inside protective coat Seed coat is maternal tissue!

Seed Development End result is seed with embryo packaged inside protective coat Seed coat is maternal tissue! Derived from epidermal tissue surrounding ovule

Seed Development Seed coat is maternal tissue! Derived from epidermal tissue surrounding ovule Determines shape of the seed!

Seed Development Seed coat is maternal tissue! Derived from epidermal tissue surrounding ovule Determines shape of the seed! Testa mutants have odd-shaped seeds

Seed Development Seed coat is maternal tissue! Derived from epidermal tissue surrounding ovule Determines shape of the seed! Testa mutants have odd-shaped seeds embryo grows to fill shape set by testa!

Seed Development End result is seed with embryo packaged inside protective coat Endosperm feeds developing embryo (3n grows faster)

Seed Development 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

Seed Development 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 Often leave a thin layer of endosperm just inside testa

Seed Development 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 Often leave a thin layer of endosperm just inside testa Seeds have three different genetic compositions!

Seed Development 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

Seed Development Embryogenesis Maturation: cell division ± ceases, but cells still expand

Seed Development Embryogenesis Maturation: cell division ± ceases, but cells still expand Controlled by different genes: viviparous mutants have normal morphogenesis but don’t mature

Seed Development Embryogenesis Maturation: cell division ± ceases, but cells still expand Controlled by different genes: viviparous mutants have normal morphogenesis but don’t mature Many morphogenesis mutants show normal maturation

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds ABA made by maternal tissue initiates this process

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds ABA made by maternal tissue initiates this process Seed [ABA] increases as enter maturation phase

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds ABA made by maternal tissue initiates this process Seed [ABA] increases as enter maturation phase Switch to ABA synthesis by embryo & endosperm during maturation

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds Storage compounds are key for seedlings and crops

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds Storage compounds are key for seedlings and crops Proteins, lipids & carbohydrates but vary widely

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds Storage compounds are key for seedlings and crops Proteins, lipids & carbohydrates but vary widely Many 2˚ metabolites

Seed Development Maturation: cell division ± ceases, but cells still expand Activate new genes for making storage compounds Storage compounds are key for seedlings and crops Proteins, lipids & carbohydrates but vary widely Next prepare for desiccation as ABA made by embryo (+endosperm) increases

Seed Development Next prepare for desiccation as ABA made by embryo (+endosperm) increases ABA peaks at mid-maturation, then declines (but not to 0)

Seed Development Next prepare for desiccation as ABA made by embryo (+endosperm) increases ABA peaks at mid-maturation, then declines (but not to 0) Blocks vivipary during maturation

Seed Development Next prepare for desiccation as ABA made by embryo (+endosperm) increases Make proteins & other molecules (eg trehalose) that help tolerate desiccation

Seed Development Next prepare for desiccation as ABA made by embryo (+endosperm) increases Make proteins & other molecules (eg trehalose) that help tolerate desiccation Next dehydrate (to 5% moisture content) and go dormant

Seed Development Next dehydrate (to 5% moisture content) and go dormant Very complex: 2 classes of dormancy Coat-imposed embryo dormancy

Seed Development Coat-imposed dormancy (maternal effect) Preventing water uptake.

Seed Development Coat-imposed dormancy (maternal effect) Preventing water uptake. Mechanical constraint

Seed Development Coat-imposed dormancy (maternal effect) Preventing water uptake. Mechanical constraint Interference with gas exchange.

Seed Development Coat-imposed dormancy (maternal effect) Preventing water uptake. Mechanical constraint Interference with gas exchange Retaining inhibitors (ABA)

Seed Development Coat-imposed dormancy (maternal effect) Preventing water uptake. Mechanical constraint Interference with gas exchange Retaining inhibitors (ABA) Inhibitor production (ABA)

Seed Development Coat-imposed dormancy (maternal effect) Preventing water uptake. Mechanical constraint Interference with gas exchange Retaining inhibitors (ABA) Inhibitor production (ABA) Embryo dormancy (Zygotic effect)

Seed Development Coat-imposed dormancy (maternal effect) Embryo dormancy (Zygotic effect) Making inhibitors (ABA?)

Seed Development Coat-imposed dormancy (maternal effect) Embryo dormancy (Zygotic effect) Making inhibitors (ABA?) Absence of activators (GA)

Seed Development Coordinated with fruit ripening: fruit’s job is to protect & disperse seed Seeds remain dormant until sense appropriate conditions: some Lotus germinated after 2000 years!

Seed germination Seeds remain dormant until sense appropriate conditions: some Lotus 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 break down hydrophobic seed coat

Seed germination Seeds remain dormant until sense appropriate conditions: Water Temperature: some seeds require vernalization = prolonged cold spell May break down hydrophobic seed coat May allow inhibitor (eg ABA) to go away

Seed germination Seeds remain dormant until sense appropriate conditions: Water Temperature: some seeds require vernalization = prolonged cold spell May break down hydrophobic seed coat May allow inhibitor (eg ABA) to go away May allow synthesis of specific RNAs

Seed germination Seeds remain dormant until sense appropriate conditions: Water Temperature: some seeds require vernalization = prolonged cold spell May break down hydrophobic seed coat May allow inhibitor (eg ABA) to go away May allow synthesis of specific RNAs Many require light: says photosynthesis is possible

Seed germination Seeds remain dormant until sense appropriate conditions: Water Temperature: some seeds require vernalization = prolonged cold spell Many require light: says photosynthesis is possible often small seeds with few reserves

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: Hormones can also trigger (or stop) germination ABA blocks it GA stimulates it

Seed germination Seeds remain dormant until sense appropriate conditions: Hormones can also trigger (or stop) germination ABA blocks it GA stimulates it Germination is a two step process Imbibition

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.

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. Seeds with endosperm pop testa first, then endosperm

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. Seeds with endosperm pop testa first, then endosperm Separate processes: can pop testa but not endosperm

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. Seeds with endosperm pop testa first, then endosperm Separate processes: can pop testa but not endosperm Testa and endosperm have different genotypes!

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. Seeds with endosperm pop testa first, then endosperm 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 Next embryo must start metabolism and cell elongation This part is sensitive to the environment, esp T & pO2 Hormones also play a complex role

Seed germination Germination is a two step process Next embryo must start metabolism and cell elongation This part is sensitive to the environment, esp T & pO2 Hormones also play a complex role GA, Ethylene and BR all stimulate

Seed germination Hormones also play a complex role GA, Ethylene and BR all stimulate ABA blocks

Seed germination Germination is a two step process 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

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

Vegetative growth Once radicle has emerged, vegetative growth begins Juvenile plants in light undergo photomorphogenesis Expand cotyledons, start making leaves & photosynthetic apparatus

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