What is Double Fertilization?
It is a type of reproduction observed in angiosperms in which the male gamete fertilizes the egg and polar nuclei of the female embryo sac. As double fertilization( one male gamete with the egg of micropylar end) and the other( second male gamete fertilizes the central cell or polar nuclei) takes place, it referred to as DOUBLE FERTILIZATION.
Define Siphonogamy
The higher plants like Gymnosperm and Angiosperm do not depend on water for their fertilization. Instead of the pollinating agents like the wind for gymnosperm and insects and others for angiosperm help in bringing the male gamete and female gamete together. Upon landing on the stigma of the pistil, the pollen tube is developed which grows long, which is referred to as pollen germination. This phenomenon is called Siphoonogamy. Nectar, and minerals like Boron help in pollen germination.