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Seeds Seeds are unique feature of plants

Explore the unique features and stages of seed development, from dormancy and germination to embryo growth and endosperm function. Learn about the crucial role of seeds in fruit development and dispersal, as well as the intricate processes that lead to successful seed formation.

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Seeds Seeds are unique feature of plants

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  1. Seeds Seeds are unique feature of plants

  2. Seeds • Seeds are unique feature of plants • Plant dispersal units

  3. 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

  4. 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

  5. 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

  6. 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

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

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

  9. Seeds (Usually) required for fruit development!

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

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

  12. 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

  13. 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

  14. 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

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

  16. 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

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

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

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

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

  21. Seed Development End result is seed with embryo packaged inside protective coat • Seed coat is maternaltissue!

  22. Seed Development End result is seed with embryo packaged inside protective coat • Seed coat is maternaltissue! • Derived from epidermal tissue surrounding ovule

  23. Seed Development • Seed coat is maternaltissue! • Derived from epidermal tissue surrounding ovule • Determines shape of the seed!

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

  25. 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!

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

  27. 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

  28. 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

  29. 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!

  30. 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

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

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

  33. 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

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

  35. 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

  36. 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

  37. 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

  38. 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

  39. 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

  40. 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

  41. 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

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

  43. 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

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

  45. 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

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

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

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

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

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

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