Usually one ovule must be fertilized for each seed that develops. In general, the sooner pollination can occur after a flower opens, the greater the likelihood that fertilization of the ovules and seed development will occur. As time elapses, the pollen may be lost to insect foragers, wind, gravity, damage by heat, moisture, or drying out. Also, processes may set in that result in the shedding of the fruit. Usually, we think of pollination in the combined sense of transfer of pollen and set of fruit or seed.
Pollination is of no value without fertilization.
Sterility, Fertility, and Compatibility Most flowers have both male and female functional parts. Some plants, however, such as asparagus, coriander, dill, or squash may have only male flowers, in which the ovaries are nonfunctional, or female flowers, in which the anthers are nonfunctional. In others, the stigma may not be receptive when the pollen is available within the flower. In such flowers, the pollen must be transferred from the male flower to the female. If the flower has both functional parts and is receptive to its own pollen, it is said to be self-fertile.