Angiosperm Reproduction

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Angiosperm Reproduction Biotechnology
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Alternation of Generations (Revisited)

• The life cycle of angiosperms and other plants
  are characterized by an alternation of
  generations, in which haploid (n) and diploid
  (2n) generations take turns producing each other
• Diploid plant (sporophyte) produces haploid
  spores by meiosis
• These haploid spores divide by mitosis, producing
  gametophytes
• These small male and female haploid plants
  (gametophytes) produce gametes
• Gametes unite through fertilization, resulting in
  a diploid zygote
• The zygote divides by mitosis, producing the new
  sporophyte

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Alternation of Generations
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A Review of Flower Structure

• Flowers are the reproductive structures of
  flowering plants
• Review structure of an idealized flower
• Male parts?
• Female parts?

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Flower Vocabulary

• Complete vs. incomplete flowers
• Complete flowers have all 4 floral parts
  (sepals, petals, stamens, carpels)
• Incomplete flowers missing at least one floral
  part
• Perfect vs. imperfect flowers
• Perfect flowers have both stamens and carpels
• Imperfect flowers are missing either stamens or
  carpels

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Flower Vocabulary

• Monoecious vs. Dioecious Plants
• Plant species are monoecious (one house) if the
  male and female parts are found on the same
  individual plant
• Plant species are dioecious (two houses) if the
  male and female parts are found on separate
  plants

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Dioecious Plants
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Pollination

• Pollination is the placing of pollen onto the
  stigma of a carpel
• Pollination is accomplished either by wind or by
  animals
• A pollen grain absorbs moisture and produces a
  pollen tube that extends down the style to the
  ovary
• The pollen grain divides by mitosis and produces
  two sperm
• One sperm cell fertilizes the egg to form the
  zygote
• The other sperm cell combines with the two polar
  bodies to form a triploid (3n) nucleus
• This cell will become the endosperm, which serves
  as a food source to the developing embryo
• This process (double fertilization) ensures that
  the endosperm (food source) will develop only in
  ovules where the egg has been fertilized

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From Ovule to Seed

• After double fertilization, the ovule will
  develop into a seed
• The seed dehydrates as it nears the end of its
  maturation
• The embryo and its food supply (cotyledons,
  endosperm or both) are enclosed by a hard,
  protective seed coat

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Seed Structure

• The radicle is the root of the embryo and where
  germination begins
• The part of the seed below the point at which the
  cotyledons are attached is called the hypocotyl
• The portion of the embryonic axis above the
  cotyledons is the epicotyl

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Seed Structure
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From Ovary to Fruit

• After double fertilization, the ovary will
  develop into a fruit enclosing the seed
• The fruit protects the seeds inside and aids in
  dispersal (by wind or animals)

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Fruits

• Simple Fruits
• A fruit derived from a single ovary
• Can be fleshy (cherry) or dry (soybean pod)
• Aggregate Fruit
• A fruit that results from a single flower that
  has several separate carpels
• Blackberries, strawberries
• Multiple Fruit
• Develops from a group of separate flowers tightly
  clustered together
• Pineapple

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Seed Dormancy

• Seed dormancy means that a seed will not
  germinate, even if sown in a favorable place,
  until a specific environmental cue causes them to
  break dormancy
• Seed dormancy increases the chances that
  germination will occur at a time and place most
  advantageous to the seedling
• How did we break dormancy in our lab??

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Stages of Seed Germination

• The seed absorbs water, causing it to expand and
  rupture its seed coat
• The embryo resumes growth, digesting the storage
  materials of the endosperm
• The radicle (embryonic root) emerges from the
  germinating seed
• The shoot tip breaks through the soil surface

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Stages of Seed Germination
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Asexual Reproduction

• Book Analogy
• Some of your fingers separate from your body, and
  eventually develop into entire copies of
  yourself!
• When plant species clone themselves by asexual
  reproduction, its known as vegetative
  reproduction

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Asexual Reproduction

• Fragmentation is the separation of a parent plant
  into parts that re-form whole plants
• This type of asexual reproduction is used to
  produce clones from cuttings (common with
  houseplants)

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Plant Biotechnology Agriculture

• Artificial Selection
• Favorable traits can be selected for by using
  selective breeding tactics
• Example maize
• Maize (corn ?) has been selectively bred to
  contain higher levels of protein for consumption
  in developing countries

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Reducing World Hunger Malnutrition

• 800,000,000 people on Earth suffer from
  nutritional deficiencies
• 40,000 people die each day of malnutrition
• Increasing food production is an important part
  of addressing this global issue
• There is a limited amount of land and water
  available for farming
• The best option is to increase the productivity
  of the land currently being farmed
• Developing transgenic plants that are resistant
  to herbicides and repel insects without the use
  of pesticides and increasing the nutritional
  quality of plants are possible with modern
  biotechnology techniques
• However, the use of biotechnology in the
  production of genetically modified plants is
  controversial