Plant Reproduction & Development

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Pant and its reproduction system

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Plant Reproduction & Development

  1. 1. By - NM Spirit T- 931-102-2687 Email- nm.sspirit@gmail.com
  2. 2. Plant reproduction Plants have two choices for reproduction:  Asexual Reproduction Sexual Reproduction Asexual reproduction – vegetative growth Portion of the plant is taken from the mature sporophyte and used to create a brand new plant this results in a genetically identical progeny this is an advantage if the plant shows superior qualities e.g. Mcintosh apple e.g. varietal grapes Disadvantage because there is no genetic variability which is crucial for the health of the plant as a species
  3. 3. Sexual reproduction – Production of sex gametes followed by their fusion and the creation of an embryo that is reliant upon the female gametophyte Diploid sporophyte produces haploid spores via meiosis The spores divide by mitosis to generate a gametophyte The gametophyte contains the small male and female haploid plants that produce gametes Fertilization results in the production of a diploid zygote which eventually becomes a diploid sporophyte via mitosis Plant reproduction
  4. 4. Angiosperms  Sexual reproduction involves flowers and seeds.  Flowering can be controlled by hormones, genes and/or environmental factors. Angiosperms produce flowers Flowers with both male and female reproductive organs are perfect flowers. Flowers that have only male or only female reproductive organs are imperfect flowers. Some angiosperms produce separate male and female flowers (imperfect flowers). Monoecious plants Dioecious plants
  5. 5. Haploid (n) Diploid (2n) Key Simplified angiosperm life cycle Germinating seed Seed Seed Simple fruit Embryo (2n) (sporophyte) Zygote (2n) FERTILIZATION Egg (n) Sperm (n) Embryo sac (n) (female gametophyte) Ovule Ovary Germinated pollen grain (n) (male gametophyte) Pollen tube Anther Mature sporophyte plant (2n) Simplified angiosperm life cycle Angiosperms
  6. 6. Flowers Flowers – Reproductive shoots of the angiosperm sporocyte. Composed of four whorls of floral organs: sepals, petals, stamens and carpels Pistil – Single carpel or a fused carpel Complete flowers have all four of these floral organs All have functional stamens and pistil Incomplete flowers lack one or more Some have functional reproductive parts Most incomplete flowers have either a stamen or a pistil Stamens – Staminate flowers Pistil – Pistillate flowers or Carpellate
  7. 7. Stamen Anther Filament An idealized flower Receptacle Petal Carpel Sepal Ovary Style Stigma Flowers
  8. 8. Flowers can be described using the following: 1. Symmetry a. Bilateral symmetry: the flower can be divided into two equal parts by an imaginary line ,e.g. orchid. b. Radial symmetry: sepals, petals, stamens and carpels radiate out from a center .e.g. daffodil. 2. Ovary location a. Superior ovary: ovary is located above the receptacle b. Inferior ovary: located within the receptacle c. Semi-inferior : in between Flowers
  9. 9. Flowers 3. Floral distribution – Vary from individual flowers to clusters of flowers called inflorescences  e.g. sunflower – center is an aggregation of incomplete flowers that do not develop  in each undeveloped flower are the male and female reproductive parts of the flower or they may be sterile 4. Reproductive variations – presence of staminate and carpellate flowers on the same plant is a monoecious plant (bisexual)  Presence of either staminate or carpellate flowers  dioecious plant (unisex) Flowers
  10. 10. Copyright reserved.  2012 The E Tutor Reproductive Structures Reproductive Floral Structures: Stamen – male reproductive structure Anther – sac where pollen in produced Filament – stalk that supports anther Carpel (Pistil) – female reproductive structure Stigma – sticky area on top of carpel that receives pollen Style – tube that connects stigma to ovary Ovary – base of carpel that contains ovule and egg sac
  11. 11. Copyright reserved.  2012 The E Tutor 11 Stamen Anther Filament Carpel Stigma Style Ovary Ovule Petal Receptacle Sepal all stamens = Androecium all carpels = Gynoecium all petals = Corolla all sepals = Calyx Male structure Female structure Reproductive Structures
  12. 12. Control of Flowering Photoperiodism – Plant response to light involving relative lengths of day and night.
  13. 13. Control of Flowering Control of Flowering  Long-day plants – Bloom when days are longest and nights are shortest (mid-summer).  Short-day plants – Bloom in spring, late summer, and autumn when days are shorter and nights are longer.  Day-neutral plants – Day-length not important for flowering.  Day length is not as critical as night length in regulation of flowering.
  14. 14. Control by light is due to a pigment in plants called phytochrome. Phytochrome – Blue-green pigment that controls various growth responses (including flowering) in plants Two forms of phytochrome: Pr – Inactive form Pfr – Active form Control of Flowering
  15. 15. Control of Flowering
  16. 16. Pollination  Pollination is the process by which pollen is placed on the stigma  Self-pollination: Pollen from a flower’s anther pollinates stigma of the same flower.  Cross-pollination: Pollen from anther of one flower pollinates another flower’s stigma. Self PollinationCross-pollination
  17. 17.  Successful pollination in many angiosperms depends on regular attraction of pollinators  Flowers & animal pollinators have coevolved resulting in specialized relationships Pollination -Bees are the most common insect pollinators
  18. 18. Flower traits that attract different pollinators are known as pollination syndromes Many ways to pollinate a female stigma 1. Wind 2. Water 3. Insect 4. Animal Pollination
  19. 19. Pollination life Cycle Pollination
  20. 20.  Biotic pollination: Pollination by animals (organisms) 80% of all pollination is biotic Entomophily – pollination by insects e.g. bees, wasps, ants, beetles, moths and butterflies Zoophily – pollination by animals e.g. birds and bats  Abiotic pollination: Pollination by non-animal factors Amenophily Pollination by wind (98% of abiotic pollination) Hydrophily Pollination by water (aquatic plants) Pollination
  21. 21.  Self- pollinization – pollen moves to the female part of the same flower or to another flower on the same plant also called autogamy self pollination is restricted to those plants that accomplish pollination without an external pollinator e.g. stamens actually grow in contact with the pistil plants adapted to self-pollinate have stamens and carpels at the same length Cleistogamy – pollination that occurs before the flower opens flower is called a cleistogamous flower these flowers MUST be self compatible or self-fertile Many crop plants are self-pollinating peas, corn and tomatoes routinely self-pollinate Pollination
  22. 22. Pollination Cross-pollination – between a pollinator and an external pollinizer also called syngamy pollen is delivered to a flower of a different plant plants adapted to cross-pollinate have taller stamens than the carpels – e.g. thrum type flower e.g. apple crops – due to the grafting of most apple species – gives rise to a genetically identical orchard Pollination
  23. 23. Fertilization  Pollen grain germinates on stigma, a pollen tube grows down the style and enters the ovule through the micropyle.  The tube cell leads the way through the pollen tube.  The generative cell divides forming 2 sperm which follow the tube cell to the micropyle.  One sperm fuses with the egg to form the zygote (2n),  The other fuses with the polar nuclei to form the endosperm (3n).  This is called double fertilization.
  24. 24. After double fertilization, the ovule develops into the seed (embryo, endosperm and integuments) Endosperm development – usually precedes embryo development the triploid nucleus divides and produces a multinucleate “supercell” with a milky consistency cytokinesis then converts the multinucleate cell into a multicellular endosperm these “naked” cells will eventually produce cell walls and the endosperm will become solid the “milk” of the coconut is an example of liquid endosperm and the “meat” is an example of a solid endosperm if the endosperm is used during the development of the cotyledons then the seed will lack an endosperm as it matures Fertilization
  25. 25. Embryo development – first mitotic division of the zygote results in an embryo splits the zygote into a basal cell and a terminal cell terminal cell gives rise to most of the embryo the basal cell continues to divide transversely and produces a thread of cells = suspensor the suspensor is the “umbilical cord” anchoring the embryo to its parent functions in the transport of nutrients to the embryo from the parent in some plants the suspensor functions in the transfer of nutrients from the endosperm Fertilization
  26. 26. Stigma Pollen tube 2 sperm Style Ovary Ovule (containing female gametophyte, or embryo sac) Micropyle Polar nuclei Egg If a pollen grain germinates, a pollen tube grows down the style toward the ovary. Pollen grain Fertilization
  27. 27. Ovule Polar nuclei Egg Two sperm about to be discharged The pollen tube discharges two sperm into the female gametophyte (embryo sac) within an ovule. One sperm fertilizes the egg, forming the zygote. The other sperm combines with the two polar nuclei of the embryo sac’s large central cell, forming a triploid cell that develops into the nutritive tissue called endosperm. Endosperm nucleus (3n) (2 polar nuclei plus sperm) Zygote (2n) (egg plus sperm) Fertilization
  28. 28. Seeds  The terminal cells divides multiple times to produces a spherical proembryo attached to the suspensor  The cotyledons begin to form as bumps on the proembryo Eudicot is heart shaped at this stage in the monocot only one of these bumps will go on to form a cotyledon  After the rudimentary cotyledons form – the embryo elongates cradled between the two cotyledons in the eudicot is the embryonic shoot apex including the shoot apical meristem at the other end of the embryo where the suspensor attaches is the root apex with its RAM
  29. 29.  The seed develops specific structures depending on whether it is a monocot or a eudicot  Eudicot – bean  elongated embryo – embryonic axis  contains two developing cotyledons attached to the embyro  below where these cotyledons attach to the embryo – hypocotyl  the hypocotyl terminates in the radicle – embryonic root  above the attachment of the cotyledons is the epicotyl – shoot tip with a pair of miniature leaves  the majority of the bean is the starch-filled cotyledons  Eudicot – castor bean  reduced cotyledons in size retain their food supply in the endosperm rather than the cotyledons  the cotyledons receive their nutrition from the endosperm and transfers it to the rest of the embryo as it grows Seeds
  30. 30. Seeds Seed coat Epicotyl Radicle Hypocotyl Cotyledons Common garden bean, a eudicot with thick cotyledons Seed coat Cotyledons Epicotyl Radicle Hypocotyl Endosperm Castor bean, a eudicot with thin cotyledons
  31. 31.  Monocot – corn kernel  single cotyledon  in the grass family (including corn and wheat) – the cotyledon is specialized and forms a scutellum  The embryo of grasses is enclosed within two shields:  Coleoptile which covers the shoot  Coleorhiza which encloses the young root  During the last stages of seed maturation – the seed dehydrates until about 5-15% total water content and becomes covered by the integuments which have hardened into a seed coat  the cotyledons and embryo become dormant Seeds
  32. 32. Maize, a monocot Coleoptile Epicotyl Radicle Hypocotyl Endosperm Pericarp fused with seed coat Coleorhiza Scutellum (cotyledon) Seeds
  33. 33. Fruits  While the seed is developing from ovules, the fruit is developing from the ovary.  Fruit = Ripened ovary + Seeds of a flowering plant.  Fruit protects the developing seeds and will participate in their dispersal using wind or animals.  Two main types of fruits: dry and fleshy  Dry fruits – The ripening of a dry fruit involves the aging and drying of the fruit tissues.  Fleshy fruits – A complex series of hormonal changes results in an enticing edible fruit that attracts animals  the fruits pulp becomes softer due to enzymes that digest components of the cell wall.  usually a color change from green to another color  organic acids and starch increase in concentration  sweet or tart fruit
  34. 34.  Fertilization of the egg triggers a series of hormonal events that triggers the development of the ovary into the fruit.  As the fruit develops, the other parts of the flower die and drop away  Tip of the pea pod is the remnant of the stigma  The fruit ripens about the same time the seed has finished its development  Accelerated through the production of ethylene  Pollination precedes fertilization – therefore fruit development is usually a sign of pollination. Fruits
  35. 35.  As the fruit develops the outer wall of the ovary thickens and develops into the pericarp Tissue that develops and surrounds a seed Develops from the wall of the ovary In some fruits the pericarp can become dry and hard and form a shell  In fleshy fruits the pericarp can be divided into several regions: Exocarp – or epicarp Tough outer skin of the fruit or the peel Mesocarp – or sarcocarp Botanical term for the succulent and fleshy middle layer of the pericarp Usually the part of the fruit that is eaten Endocarp – hard inner layer of the pericarp of some fruits that contains the seed Fruits
  36. 36. Types of fruits  Several types of fruits depending on their developmental origin 1. Simple: derived from a single carpel or several fused carpels within one pistil Can be either fleshy or dry The dry fruits can either be dehiscent (opening to discharge seeds) or indehiscent (not opening to discharge seeds) If the pericarp is fleshy – fruit is known as a simple fleshy fruit e.g. apple, peach, pea, wheat, coconut, carrot, radish, tomato. 2. Aggregate – results from a single flower that has more than one separate carpel with each forming a separate “fruitlet” Develops from multiple simple pistils with one carpel each The fruit is frequently called a “druplet” (raspberry) or a bramble (blackberry).
  37. 37. Types of fruits Stamen Stigma Ovary Pea flower Ovule Seed Pea fruit Simple fruit Stamen Stigma Ovary Raspberry flower Aggregate fruit Stamen Carpels Carpel (fruitlet) Raspberry fruit
  38. 38. 3. Multiple – develops from an influorescence (a group of flowers tightly clustered together) – the walls of the ovaries thicken and fuse together  e.g. pineapple, mulberry, breadfruit  There are fruits in which structures other than the ovary contribute to the formation of the fruit  These fruits are called accessory fruits or false fruits Types of fruits Pineapple inflorescence Multiple fruit Flower Each segment develops from the carpel of one flower Pineapple fruit
  39. 39. Seedless fruits  Seedlessness is an important feature of fruit crops like bananas, pineapples, grapes, watermelons, some citrus fruits (navel oranges, tangerines).  In some species, seedlessness is the result of parthenocarpy: Fruits set without fertilization May or may not require pollination  Some fruits will become seedless if the plant does not undergo pollination but will develop seeds if pollination takes place and results in fertilization within the ovules – e.g. pineapple, cucumber
  40. 40. Seed Germination  As a seed matures it dehydrates and enters a dormancy phase – low metabolic rate in the embryo and a suspension of its growth and development.  Conditions required to break this dormancy varies from plant to plant. – e.g. once they reach a suitable environment. – e.g. some require a specific environmental cue.  Seed dormancy increases the chances that the seed will germinate under favorable conditions.  Environmental conditions  Desert plants – require substantial amounts of water.  Trees – heat provided by fires.  Extended exposure to cold.  Lettuce – requires increased light.
  41. 41.  Germination depends on the physical process called imbibitions. uptake of water due to the lower water potential of the dry seed causes the seed to expand and rupture its coat also triggers metabolic events in the embryo that enables it resume its development as the embryo grows it makes digestive enzymes which digests away the stored foot in the seed (endosperm or cotyledons) first organ to emerge is the embryonic root – the radicle the shoot tip then forms and breaks through the soil surface Seed Germination
  42. 42.  In many eudicots and beans – a hook forms in the hypocotyl and this hook is pushed through the soil – stimulated by light to straighten which raises the cotyledons and the epicotyl.  The shoot apex is actually pulled upward rather than being pushed tip first through the abrasive soil.  The epicotyl spreads its first leaves which are called true leaves as apposed to the “seed leaves” or the cotyledons.  In monocots breaking ground is accomplished by the coleoptile.  The sheath enclosing the coleoptile pushes upward through the soil and into the air.  The shoot tip grows through the tunnel forming within the growing coleoptile.  The shoot then breaks through the tip of the coleoptile. Seed Germination
  43. 43. Seed Germination Foliage leaves Cotyledon Cotyledon Hypocotyl Hypocotyl Radicle Seed coat Hypocotyl Cotyledon Epicotyl Common garden bean
  44. 44. The End Contact Us For More Information +91-931-102-2687

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