EMBRYO DEVELOPMENT

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EMBRYO DEVELOPMENT
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• Embryo develops from zygote at the micropylar
  end of embryo sac.
• The nutrition for development is provide by
  endosperm.
• The zygote divides to form pre-embryo.
• The different stages of the developing
  pro-embryo are globular and heart shaped embryo ,
  which finally forms mature embryo.

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EMBRYOGENY IN DICOTS

• The zygote undergoes transverse division forming
  a large basal cell and a small apical or terminal
  cell.
• The large basal cell enlarges and undergoes
  transverse division to form a group of 6-10cells
  called suspensor.
• The first cell of the suspensor towards the
  micropylar end is called haustorium, whereas the
  last cell of the suspensor toward the chalazal
  end is called is hypophysis that later develop
  into radical.

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• The smaller terminal or apical cell
  undergoes one vertical division. The two cells
  formed from terminal cell divide by transverse
  division thus forming four embryonic cell(
  quadrant stage ).
• Finally these four cell divide vertically
  forming 8 celled pre-embryo (octate stage). Four
  cells at the apex give rise to plumule and
  another four give rise to hypocotyl except its
  tip.

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STRUCTURE OF DICOTYLEDONOUS EMBRYO

• A typical dicotyledonous embryo consists of an
  embryonic axis and two cotyledons.
• The portion of embryonic axis above the level
  of cotyledons is the epicotyl, which develops
  into plumule or stem tip.
• The cylindrical portion below the level of
  cotyledon is hypo, which develops into radical or
  root tip .
• The root tip is often covered with a root cap

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A typical monocotyledonous embryo

• A typical monocotyledonous embryo consists of
  one cotyledon.
• The cotyledon is situated on one side (lateral)
  embryonic axis and is called scutellum.
• The radical and root cap are situated at lower
  end of embryonic axis in an undifferentiated
  sheath called coleorrhiza.
• The shot apex and few leaf primordia is enclosed
  in hollow foliar structure in epicotyl region
  called coleoptile.
• The portion of the embryonic axis above the
  level of attachment of scutellum is called
  epicotyl.