Understanding Sexual Reproduction in Plants

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Lesson 1

• Understanding Sexual Reproduction in Plants

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Next Generation Science/Common Core Standards
Addressed!

• HS-LS1-Construct an explanation based on evidence
  for how the structure of DNA determines the
  structure of proteins which carry out the
  essential functions of life through systems of
  specialized cells. Assessment Boundary
  Assessment does not include identification of
  specific cell or tissue types, whole body
  systems, specific protein structures and
  functions, or the biochemistry of protein
  synthesis.
• WHST.9-12.7 Conduct short as well as more
  sustained research projects to answer a question
  (including a self generated question) or solve a
  problem narrow or broaden the inquiry when
  appropriate synthesize multiple sources on the
  subject, demonstrating understanding of the
  subject under investigation. (HS-LS1-3)
• HSSIC.A.1 Understand statistics as a process for
  making inferences about population parameters
  based on a random sample from that population.
  (HS-LS2-6)

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Bell Work!

• 1. Discuss the importance of plant propagation
• 2. Explain the difference between sexual and
  asexual reproduction
• 3. Identify the major parts of a seed
• 4. List the function of each major part of a seed

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Terms!

• Cotyledon
• Cross pollination
• Diploid
• Embryo
• Endosperm
• Epicotyl (plumule)
• Fertilization
• Gametes
• Genes

• Haploid
• Hybrids
• Hypocotyl
• Pollination
• Radicle
• Seed
• Seed coat
• Self pollination
• Sexual reproduction
• Zygote

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Interest Approach

• Look at the sample of plants that I have brought
  in for you.
• What are the two categories of plants that are
  displayed?
• How important do you think flowers are to a
  plant?
• How are plants more successful at reproduction
  than animals?

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What Would Happen if Plants Did Not Have the
Ability to Reproduce?

• Plants are essential for life as we know it on
  earth
• They are the ecological producers of our planet
• They produce food and shelter for other
  organisms, produce oxygen to support animal
  respiration, and enrich our environment
• Throughout history people have relied on seeds
  and plant parts to grow new plants for food and
  fiber. Livestock production would be impossible
  without plants!

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• In more recent times, knowledge of plant
  reproduction has resulted in the development of
  plant hybrids that have enabled large scale
  agricultural production of food and fiber plants

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How Is Sexual Reproduction Different From Asexual
Reproduction?

• Sexual reproduction occurs when the male sperm
  carried in the pollen unites with the female egg
  within a flower
• Most plants reproduce their own kind in nature by
  seeds that are the result of sexual reproduction
• The male sex cell (sperm) and the female sex cell
  (egg) are known as gametes
• The union of gametes produces the seed that
  contains the embryo plant and stores food

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• Both the male sperm and the female egg contribute
  genetic information to the new embryo plant
• This results in new combinations of genes
  producing new traits that add vigor to the
  offspring
• The offspring resulting from this new combination
  of genes is known as a hybrid
• People have greatly improved agricultural crops
  through hundreds of years of hybridization

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• The genes, made from DNA, are located in
  chromosomes
• Normal cells contain a pair of chromosomes and
  are said to be diploid
• Reproductive cells, the egg and sperm, contain a
  single chromosome and are said to be haploid

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• Fertilization unites the single chromosome in the
  sperm nucleus with the single chromosome in the
  egg nucleus
• This enables the fertilized egg or zygote to have
  a complete pair of chromosomes (diploid)
• Plant fertilization is unique because the sperm
  contains two nuclei
• Causes the plant to become double fertilized
• One sperm nucleus unites with the egg nuclei to
  produce a zygote
• The second sperm nucleus unites with the nuclei
  of the embryo sac that develops into the endosperm

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Fertilization Process
Pollen
Stigma
Two sperm nuclei
Ovary
Pollen tube
Egg
Second nucleus
Egg nucleus
One sperm fertilizes egg
One sperm fertilizes second nucleus to form
endosperm
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• Pollination is the transfer of the male sperm
  carried in the pollen to the female part of the
  flower, the stigma
• Plants rely on insects, wind and water to
  transfer the pollen to the stigma
• In addition, plants depend on animals to help
  with this process
• Birds, insects, bats and other animals are
  attracted to brightly colored, scented flowers
• These animals transfer pollen from the anthers of
  the flowers they visit to the stigmas of other
  flowers

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Pollination
Pollen grains (contain sperm)
Stigma
Ovule
Egg cell
A bat is covered with pollen from this flower.
It will transfer this pollen to another flower
when it searches for more nectar.
Ovary
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Pollination
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Pollination
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Pollination
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Types of Pollination

• A. When the pollen of a plant pollinates a
  flower on the same plant, it is called
  self-pollination
• Many plants have this ability, others do not
• B. When the pollen of a plant pollinates the
  flower on another plant of the same species, it
  is said to be cross-pollination

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What Are the Major Parts of a Seed Where Are
They Located?

• A seed is a living entity that serves as a bridge
  between generations of a plant
• It is formed in the pistil of the flower and
  develops from the ovule following fertilization
• As the fertilized egg (zygote) grows and
  develops, it becomes the embryo of the seed

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Parts of the Embryo

• The embryo contains the root, stem and leaf of a
  complete plant
• In addition to this, it also contains stored food
  to support development and growth of the embryo
• The seeds of dicot plants have food stored
  cotyledons. In monocot seeds, most food is found
  in the endosperm
• The embryos root is called the radicle, the stem
  the hypocotyl and the leaf the epicotyl
• Surrounding the embryo endosperm is a
  protective seed coat

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Embryo Parts
Seed coat
Hypocotyl
Epicotyl
Cotyledons
Seed coat
Endosperm
Epicotyl
Hypocotyl
Cotyledon
Radicle
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What Is the Function of Each Major Part of a Seed?

• Each part of the seed has a specific function to
  help ensure that a healthy new plant will emerge
  from the seed
• The seed is a living entity which contains the
  embryo plant everything necessary for its
  growth development
• Dicot plants (soybean, pea, oak) have two
  cotyledons while monocots (corn, coconut, lilies)
  have only one cotyledon in its seed

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Seed Parts Functions
Radicle Lower part of the hypocotyl forms the first root first to emerge from the seed
Hypocotyl Develops into the true stem
Epicotyl Above the hypocotyl develops into a pair of small leaves Tip is sometimes called the plumule it is the terminal bud of the first shoot to emerge form the seed
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Endosperm Found in monocots in an area of high concentration of food food source for the embryo
Cotyledon Stores food absorbed from the endosperm when the seed is formed provides energy until the plant produces its own food
Seed coat Surrounds the seed and protects it from injury and dehydration
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Summary

• Why are plants essential on earth?
• How is sexual reproduction different from asexual
  reproduction?
• What is another name for the sex cells of a
  plant?
• How is a haploid gene different from a diploid
  gene?
• Explain the process of pollination. What are the
  two types?

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Summary Continued

• How does fertilization in a plant occur?
• What part of the seed is the primary root?
• What is the function of a cotyledon?
• What part of the plant develops into the true
  stem?
• How is a monocot different from a dicot?
• What protects the seed before it germinates?

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The End!