Explanation

Fusion of male and female gametes (i.e, syngamy) in seed plants, occurs through siphonogamy as the gametes are carried through the pollen tube. Pollen tube can enter the ovule by three methods: 1.Porogamy- through micropyle 2.Chalazogamy- through chalaza 3.Mesogamy –pollen tube penetrates laterally through integuments or funiculus.