Sexual & Asexual Reproduction

1. Sexual & Asexual Reproduction Pollination and Fertilization: Presentation 2 of 3

2. Pollination • Pollination occurs when mature pollen grains (male sex cells from the stamen) come into contact with the moist, sticky surface of a flower stigma (female flower part). stigma stamen

3. Pollen grains transfer to the stigmas of flowers by means of: • gravity, • insects, • wind, and • animals.

4. Self-pollination occurs when pollen comes into contact with a stigma within the same flower or other flowers on the same plant. • Cross-pollination occurs when pollen from the flower of one plant transfers to stigmas of flowers on another plant.

6. After a pollen grain anchors on the moist, sticky surface of a flower stigma, it germinates and produces a pollen tube. • The pollen tube grows down through the style and into the ovary where it eventually reaches an ovule

8. Fertilization • In angiosperms (flowering plants), two haploid nuclei or sperm cells are released from the pollen tube.

9. Double Fertilization is known as, one sperm cell unites with the egg cell in the ovule to form a zygote (diploid), while the second sperm cell unites with two separate polar nuclei to form a primary endosperm nucleus (triploid).

11. The zygote, formed through the union of the sperm cell and egg cell, proceeds through cell division and develops into a seed embryo. • The primary endosperm nucleus develops to form a food source to be used by the embryonic plant during seed germination.

12. For each seed a plant produces, a separate grain of pollen must reach and unite with an ovule.