Plant Seed Germination, Growth and Development

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Plant Seed Germination, Growth and Development

• Biology Accelerated 2006

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Stages of Development

• Zygote divides to become a spherical mass of
  cells which develop into the embryo.
• Differentiation begins- small bumps form and
  become the cotyledons.
• Elongation of the embryo occurs-
• Cells differentiate into specialized structures
• Cells between the cotyledons become the embryonic
  shoot.
• Embryonic roots develop.

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Development Terms

• Endosperm-
• .Contains nutrients from mother plant
• Cotyledons-
• Seed leaves, emerge first and can carry on
  photosynthesis until true leaves develop.
• Epicotyl- immature leaf
• Hypocotyle- First root
• Radicle- tip of the immature root
• Embryonic Shoot- becomes the stem and leaves.
• Apical meristems- cells which divide.

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• Seed coat- formed from maternal flower tissue,
  encloses the endosperm and embryo and provides
  protection.
• Germination- sprouting of the seed.
• Primary Growth- growth from the meristems present
  in the embryo.
• Node- point at which a leaf emerges.
• Root cap- mass of tough tissue which covers and
  protects the apical meristem of the root.
• Secondary Growth- increase in diameter in older
  cells.
• Vascular cambium- meristem tissue near the outer
  surface of roots and stems, produces xylem and
  phloem.

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• Epidermis- surface cells.
• Cuticle- hydrophobic cuticle of wax that keep
  moisture in, pathogens and micro-organisms out.
• Vascular tissue- tissue which becomes xylem and
  phloem.
• Ground tissue- other tissue which give shape and
  internal support.

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• Xylem- Carry water and minerals, composed of
  thick cells, wood, provide support for plant.
• Phloem- cary food- dissolved sugars and amino
  acids.
• Cork cambium- produces bark which provides
  protection from dehydration and other organisms.
• Pericycle- cylinder of meristem that surrounds
  xylem and phloem in the root and give rise to
  secondary roots.

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Etymology

• Endo- inside (Greek)
• Sperm- seed (Greek)
• Xyle- wood
• Epi- above
• Hypo- less, below
• Peri- around

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Seed Germination

• When water, oxygen, and temperature are right
  metabolism, growth and development resume.
• Enzymes begin to digest the stored food in
  endosperm and cotyledon.
• Nutrients move to the growing regions.
• Cell respiration speeds up.
• Absorbed H2O restores turgor pressure.
• Cells expand.
• Seed coat fractures, embryonic root emerges.
• Shoot grows up.

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Primary and Secondary Growth

• Cell division in the apical meristem begins.
• Nutrients from the cotyledon and endosperm allow
  the plant to grow until photosynthesis begins.
• Roots anchor the plant and begin taking in
  minerals and water.
• A root cap protects the apical meristem of the
  root as it grows through the soil.
• Three major tissue types emerge (eidermis,
  vascular tissue, ground tissue.

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• Growth of the cell wall
• Rate and orientation of cell division.

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