Definition

1. Noun:
   • The larger of the two types of spore produced by heterosporous plants: A megaspore is a haploid reproductive cell that is typically larger than the microspore. It is produced within an ovule and develops into a female gametophyte, which produces egg cells.

Examples of Usage

• Noun:
  • In ferns and seed plants, the megaspore is the structure that gives rise to the female gametophyte.
  • The development of the embryo sac begins with a single functional megaspore.

Advanced Usage

• "Functional megaspore": In many plants, only one of several megaspores produced survives and develops into the female gametophyte; this is termed the functional megaspore.
  • After meiosis, the chalazal megaspore often becomes the functional megaspore.

Variants and Related Words

• Megasporangium (n): The sporangium (structure) in which megaspores are formed.
  • The ovule is considered a megasporangium in seed plants.
• Megasporocyte (n): Also called a megaspore mother cell; the diploid cell that undergoes meiosis to produce (typically four) haploid megaspores.
  • The megasporocyte divides meiotically to form a tetrad of megaspores.
• Megasporogenesis (n): The process of megaspore formation.
  • Megasporogenesis involves the meiotic division of the megasporocyte.

Synonyms

• Macrospore: An older, synonymous term for megaspore.

Related Terms (Contextual)

• Microspore (n): The smaller of the two spore types in heterosporous plants; it develops into a male gametophyte (pollen grain).
  • The plant produces both microspores and megaspores.
• Heterospory (n): The production of two distinct types of spores (microspores and megaspores).
  • Heterospory is a characteristic feature of all seed plants and some pteridophytes.

Noun

1. larger of the two types of spore produced in heterosporous plants; develops in ovule into a female gametophyte