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Questions and Answers
What does the basal cell in the embryonic development of monocots become?
What does the basal cell in the embryonic development of monocots become?
What is the result of the quadrants dividing transversely in the monocot embryonic development?
What is the result of the quadrants dividing transversely in the monocot embryonic development?
Which of the following structures is formed from the lowermost cell of the three-celled suspensor?
Which of the following structures is formed from the lowermost cell of the three-celled suspensor?
In monocots, what ultimately develops from the octants during embryonic development?
In monocots, what ultimately develops from the octants during embryonic development?
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What is the role of periclinal division in the embryonic development of monocots?
What is the role of periclinal division in the embryonic development of monocots?
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What is the initial state of the fertilized egg before developing into an embryo?
What is the initial state of the fertilized egg before developing into an embryo?
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During the formation of the proembryo, which cell is positioned towards the micropyle?
During the formation of the proembryo, which cell is positioned towards the micropyle?
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What stage follows the quadrant stage in dicot embryo development?
What stage follows the quadrant stage in dicot embryo development?
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Which part of the developed embryo ultimately gives rise to the root cap, epidermis, and cortex of the root?
Which part of the developed embryo ultimately gives rise to the root cap, epidermis, and cortex of the root?
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In the mature dicot embryo, what shape does it resemble?
In the mature dicot embryo, what shape does it resemble?
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What is the embryonal axis portion above the cotyledon attachment called?
What is the embryonal axis portion above the cotyledon attachment called?
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Which structure develops from the outer eight cells of the octant stage?
Which structure develops from the outer eight cells of the octant stage?
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What is the process called when the basal cell divides several times to form a part of the embryo?
What is the process called when the basal cell divides several times to form a part of the embryo?
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Study Notes
Dicot and Monocot Embryo
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Dicot Embryo Development:
- After fertilization, the fertilized egg becomes a zygote, which develops into an embryo.
- The oospore rests for a period before development, ranging from hours to months.
- The zygote (oospore) divides immediately after the primary endosperm nucleus (PEN) divides.
- The zygote divides transversely to form a two-celled proembryo.
- The cell towards the micropyle is the basal cell; the other is the terminal cell.
- The basal cell forms a suspensor.
- The terminal cell divides longitudinally twice, forming a four-celled structure, the quadrant stage.
- The four cells further divide transversely, forming an octant stage (eight cells arranged in two tiers of four).
- The lower tier gives rise to stem tip and cotyledons, while the upper tier forms the hypocotyl.
- Periclinal division in the octant cells produces eight outer and eight inner cells.
- The eight outer cells form the dermatogen, which develops into the epidermis.
- The eight inner cells form the periblem and plerome, developing into the cortex and stele.
- The basal cell forms a suspensor made of six to ten cells.
- The lowest cell of the suspensor is the hypophysis, which produces root cap, epidermis, and cortex.
- The cotyledons curve, and the embryo is horse-shoe shaped.
- The stem tip is terminal, and cotyledons are lateral in the mature embryo.
- Embryo development stages: globular, heart-shaped, and horse-shoe shaped, eventually maturing.
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Monocot Embryo Development:
- There is no essential difference in the early cell divisions between monocots and dicots.
- Mature embryos differ significantly between monocots and dicots.
- Sagittaria sagittifolia embryogeny is used as an example.
- The zygote divides transversely to form a terminal and basal cell.
- The basal cell does not divide, but becomes large and vesicular.
- The terminal cell divides transversely into two cells.
- The lower cell divides vertically, forming juxtaposed cells, and the middle cell also divides transversely.
- The two-cell stage subdivides into quadrants.
- The cell next to the quadrants and the upper vesicular cell divide vertically and transversely, respectively.
- The quadrants divide transversely to form octants (eight cells).
- Periclinal division results in the formation of the dermatogen.
- Periblem and plerome are also differentiated.
- The octants form a single terminal cotyledon.
- The lowermost cell of the three-celled suspensor divides vertically, producing the plumule or stem tip.
- The cells R form the radicle.
- Three to six upper cells form the suspensor.
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