Assertion: male gametophyte | /r/HasProperty | pollen grains
Facets:
value: in angiosperms
type: LOCATION
Source sentences:
text: Spore mother cells in the microsporangia divide by meiosis to form haploid microspores that develop further by two mitotic divisions into immature male gametophytes (pollen grains).
text: In all gymnosperms, the male gametophyte (pollen grain) reaches the female reproductive structure helped by wind or animals.
text: In angiosperms the male gametophyte is the pollen grain, and the female gametophyte the embryo sac.
text: A number of parts of the reproductive process are common to both angiosperms and gymnosperms: (1) they produce seeds at maturity; (2) the megasporangium, unlike that of heterosporous seedless plants, is covered by one or two cellular layers called integuments and is termed an ovule; (3) there is a minute passageway, or micropyle, through the integuments; (4) the ovule matures as a seed; (5) only one megasporocyte is present and undergoes meiosis in the megasporangium to produce four megaspores, only one of which usually is functional; (6) the megaspore is never discharged from its megasporangium and ovule; (7) one female gametophyte is produced within each megasporangium and ovule; (8) the microspores begin their development into male gametophytes while still enclosed in the microsporangia; (9) as they mature, the male gametophytes, which are contained within the microspore wall and are termed pollen grains, develop a tube that conveys sperm to the egg cell; (10) union of sperm and egg and development of an embryonic sporophyte from the zygote occur within the female gametophyte (sometimes called the “embryo sac”), which is covered by the remains of the megasporangium and by integuments; (11) as the embryo develops, the ovule matures as a seed.
text: At this stage the male gametophyte (called a pollen grain) is shed and transported by wind or insects.
text: The anther produces male gametophytes which are pollen grains, which attach to the stigma on top of a carpel, in which the female gametophytes (inside ovules) are located.
text: The gymnosperm male gametophytes (pollen grains) are carried by wind to a female cone and are drawn into a tiny opening on the ovule called the micropyle.
text: This male cone, shown in cross section, has approximately 20 microsporophylls, each of which produces hundreds of male gametophytes (pollen grains).
text: In gymnosperms and angiosperms it plays a dominant role, ensuring the development of greatly reduced gametophytes (male gametophytes are pollen grains; female ones are the primary endosperm and the embryo sac).
text: The male gametophyte (pollen grain) develops within the anther and comprises two sperm cells encased within a vegetative cell (McCormick, 2004).
text: In angiosperms the male gametophyte is the pollen grain, and the female gametophyte the embryo sac.