Training Manual Development Of Cultivars And Seed ... - icrisat

along the panicle branch.
Fertilization
Pollen grains germinate as soon as they come in contact with a receptive stigma; the pollen tubes grow
through the stigmatic papillae down to the ovary through the stylar region. Only one pollen tube succeeds
in reaching the micropyle. The sperm nucleus divides into two, one of which fertilizes the egg cell to give
rise to the embryo (2n = 20 chromosomes in sorghum), the other joins the two polar nuclei to form the
endosperm (3n = 30 chromosomes, i.e., 20 from the female parent and 10 from the male parent). This
process of embryo formation by the union of egg nucleus and sperm nucleus is called fertilization. The
glumes close shortly after pollination. The ovule begins to develop as a light green, almost cream-colored
sphere, and about 10 days after pollination, it becomes bigger and turns dark green. The development
of the embryo and endosperm continues for another 30 days when the seed reaches physiological
maturity with the hilum region (a spot on the seed through which the seed receives nourishment of the
plant) becoming black. During the development, the seed passes through milk, early-dough, and latedough
stages. The dried-up style may persist in some seeds up to physiological maturity (House 1985).
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