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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
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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 maternaltissue!
Seed Development End result is seed with embryo packaged inside protective coat • Seed coat is maternaltissue! • Derived from epidermal tissue surrounding ovule
Seed Development • Seed coat is maternaltissue! • Derived from epidermal tissue surrounding ovule • Determines shape of the seed!
Seed Development • Seed coat is maternaltissue! • Derived from epidermal tissue surrounding ovule • Determines shape of the seed! • Testa mutants have odd-shaped seeds
Seed Development • Seed coat is maternaltissue! • 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)