Macrospores

Macrospores are a botanical term referring to the larger of the two types of spores produced by heterosporous plants. These plants, which include seed plants, some ferns, and some lycophytes, produce two distinct spore types. The macrospore develops into the female gametophyte, which typically contains the egg cell. In contrast, the microspore is the smaller spore and develops into the male gametophyte, producing sperm. The formation of macrospores and microspores is a crucial step in the life cycle of these plants, enabling sexual reproduction. The macrospore is usually retained within the parent sporophyte, a characteristic that is a precursor to the evolution of seeds. After fertilization, the embryo develops within the ovule, which originates from the megasporangium containing the macrospore. The size difference between macrospores and microspores is a key feature distinguishing heterospory from homospory, where only one type of spore is produced.