Definition

1. Noun:
   • The larger of the two types of spores produced by heterosporous plants: A macrospore is a reproductive cell that is larger than its counterpart (the microspore) and is produced by plants exhibiting heterospory. It develops within an ovule to give rise to the female gametophyte, which produces egg cells.

Examples of Usage

• Noun:
  • In ferns like Selaginella, the macrospore germinates to form the female gametophyte.
  • The development of the embryo sac in seed plants begins with a functional macrospore.

Advanced Usage

• "Functional macrospore": In many plants, only one of several macrospores produced survives and develops into the female gametophyte; this surviving cell is termed the functional macrospore.
  • After meiosis, only one of the four potential macrospores becomes the functional macrospore.

Variants and Related Words

• Megaspore (n): A fully synonymous term for macrospore. "Megaspore" is more commonly used in botanical texts.
  • The terms 'macrospore' and 'megaspore' are often used interchangeably.
• Microspore (n): The smaller spore type in heterosporous plants, which develops into the male gametophyte.
  • The plant produces both microspores and macrospores.
• Heterosporous (adj): Describing plants that produce two distinct sizes of spores (microspores and macrospores).
  • Selaginella is a heterosporous plant.

Synonyms

• Megaspore: The larger spore; the direct synonym.

Related Terms and Concepts

• Ovule (n): The structure in seed plants that contains the macrospore and develops into a seed after fertilization.
  • The macrospore is located within the ovule.
• Female gametophyte (n): The multicellular haploid structure that develops from a macrospore and produces the egg cell.
  • The macrospore undergoes mitosis to form the female gametophyte.

Noun

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