AP BIOLOGY

Detailed explanation-1: -When the pollen grain lands on the stigma, chemical communication occurs between the pollen grain and the pistil, helping the pistil recognize the right type of pollen. After acceptance, pollen begins to germinate and the pollen tube develops towards the ovary carrying the male gamete.

Detailed explanation-2: -After pollen lands on the stigma, it initiates pollen tube formation. Pollen tubes are channels which grow down the length of the style to the ovules. After a pollen grain travels down a pollen tube it intercepts an ovule, fertilizes the female germ cells and initiates seed development.

Detailed explanation-3: -When pollen gran falls on stigma, it germinates on stigma and produce pollen tube which enters into the ovule release 2 male gametes and fuse with the ovule to form a seed.

Detailed explanation-4: -Pollination is the act of transferring pollen grains from the male anther of a flower to the female stigma.

Detailed explanation-5: -When pollen grains of a flower reaches the stigma of the same flower, it is called self-pollination or Autogamy.