Fusion of Gametes in Flowers: Fertilization, Embryogenesis & Somatic Variation

Fertilization in Pteridophytes

Male gametes (ciliated) require water to reach archegonia. Zygote formation leads to embryo with foot, shoot apex, first root—not bipolar like seed plants. Division patterns (horizontal/vertical) create exoscopic/endoscopic embryos, with/without suspensor.

Somatic Embryogenesis: Nature's Cloning

Embryos from non-gametic cells—no fertilization. Occurs spontaneously in 60+ families (citrus, legumes, grasses). Both zygotic and somatic can coexist in seeds. In vitro: first achieved in carrot (1958); now 30+ species, including alfalfa and forest trees, commercially propagated.

Process & Applications

Explants: root/shoot tips, hypocotyls, petioles, young leaves, meristematic tissues. Two pathways: direct (predetermined) or indirect (via callus induction). Yields synthetic seeds—encapsulated, storable embryos. Advantages: mass propagation, complete structures. Drawbacks: abnormalities, polyembryony, premature germination.