Life cycle of a typical angiosperm
The angiosperm life
cycle consists of a sporophyte phase and a gametophyte phase. The cells
of a sporophyte body have a full complement of chromosomes (i.e., the
cells are diploid, or 2n); the sporophyte is the typical plant
body that one sees when one looks at an angiosperm. The gametophyte
arises when cells of the sporophyte, in preparation for reproduction,
undergo meiotic division and produce reproductive cells that have only
half the number of chromosomes (i.e., haploid, or n). A
two-celled microgametophyte (called a pollen grain) germinates into a
pollen tube and through division produces the haploid sperm. An
eight-celled megagametophyte (called the embryo sac)
produces the egg.
Fertilization occurs with the fusion of a sperm with an egg to produce a
zygote, which eventually develops into an embryo. After fertilization,
the ovule develops into a seed, and the ovary develops into a fruit.
