Question:
What do you mean by the mechanism in which the embryo develops from an unreduced egg in an embryo sac from a nuclear cell?
What do you mean by the mechanism in which the embryo develops from an unreduced egg in an embryo sac from a nuclear cell?
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Remember: "Apo-" means "away from" and "spore" refers to the gametophyte generation. In Apospory, the embryo sac originates from a non-reproductive (somatic) cell like the nucellus, rather than a spore-forming cell.
Updated On: Aug 7, 2026
- Adventitious embryony
- Apogamy
- Apospory
- Diplospory
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Question:
The question asks to identify a specific form of apomixis (asexual reproduction through seeds) where an embryo develops from an unreduced (diploid) egg cell within an embryo sac that was formed from a nucellar cell (often referred to as a "nuclear cell" in some literature or due to typographical errors in exams). This process bypasses the normal meiotic reduction of chromosomes.
Detailed Explanation:
• Apomixis Overview: Apomixis is a reproductive process in plants that mimics sexual reproduction but occurs without fertilization. It results in offspring that are genetically identical to the parent. It is broadly categorized into vegetative propagation and agamospermy (seed-based).
• Apospory: This is a type of gametophytic apomixis. In this mechanism, a cell from the nucellus (the tissue inside the ovule) or the integument develops into a diploid (unreduced) embryo sac without undergoing meiosis. The egg cell inside this embryo sac is diploid. When the embryo develops from this unreduced egg without fertilization (parthenogenesis), the whole process is termed apospory.
• Diplospory: In contrast, diplospory occurs when the megaspore mother cell (MMC) itself fails to undergo meiosis and develops directly into a diploid embryo sac. While the outcome (an unreduced embryo sac) is similar, the starting cell is different (MMC for diplospory vs. nucellar cell for apospory).
• Adventitious Embryony: Here, the embryo develops directly from the diploid cells of the nucellus or integuments, bypassing the formation of an embryo sac entirely.
• Apogamy: This refers to the development of an embryo from a cell of the embryo sac other than the egg cell (such as synergids or antipodal cells).
Step 2: Final Answer:
Based on the origin from a nucellar (nuclear) cell into an embryo sac containing an unreduced egg, the mechanism is apospory.
The question asks to identify a specific form of apomixis (asexual reproduction through seeds) where an embryo develops from an unreduced (diploid) egg cell within an embryo sac that was formed from a nucellar cell (often referred to as a "nuclear cell" in some literature or due to typographical errors in exams). This process bypasses the normal meiotic reduction of chromosomes.
Detailed Explanation:
• Apomixis Overview: Apomixis is a reproductive process in plants that mimics sexual reproduction but occurs without fertilization. It results in offspring that are genetically identical to the parent. It is broadly categorized into vegetative propagation and agamospermy (seed-based).
• Apospory: This is a type of gametophytic apomixis. In this mechanism, a cell from the nucellus (the tissue inside the ovule) or the integument develops into a diploid (unreduced) embryo sac without undergoing meiosis. The egg cell inside this embryo sac is diploid. When the embryo develops from this unreduced egg without fertilization (parthenogenesis), the whole process is termed apospory.
• Diplospory: In contrast, diplospory occurs when the megaspore mother cell (MMC) itself fails to undergo meiosis and develops directly into a diploid embryo sac. While the outcome (an unreduced embryo sac) is similar, the starting cell is different (MMC for diplospory vs. nucellar cell for apospory).
• Adventitious Embryony: Here, the embryo develops directly from the diploid cells of the nucellus or integuments, bypassing the formation of an embryo sac entirely.
• Apogamy: This refers to the development of an embryo from a cell of the embryo sac other than the egg cell (such as synergids or antipodal cells).
Step 2: Final Answer:
Based on the origin from a nucellar (nuclear) cell into an embryo sac containing an unreduced egg, the mechanism is apospory.
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