Fertilisation Flashcards
What is the first stage of fertilisation?
A compatible pollen grain lands on the stigma and it germinates in sucrose solution secreted by the stigma, forming a pollen tube from the tube nucleus.
What is the second stage in fertilisation.
The pollen tube nucleus is at the tip of the tube with 2 male nuclei behind it. The pollen tube grows out of the pollen grain through a gap in the cell wall called a pit, down the style up a gradient of chemoattractants like GABA from the ovule.
What is the third stage of fertilisation?
The pollen tube nucleus codes for the production of hydrolases including cellulases and proteases and it digests it’s way through the style tissues, using the products for growth.
What is the fourth stage of fertilisation?
The pollen tube grows through the micropyle which is a gap in the integumunts and passes into the embryo sac.
What is the fifth stage of fertilisation?
The pollen tube nucleus disintegrates and the tip of it opens releasing the 2 male gametes into the embryo sac, where it fuses with the female gamete to make a diploid zygote.
What happens to the second male gamete?
It fuses with the diploid polar nucleus to form a Triploid nucleus, which is the endosperm nucleus. This divides repeatedly by mitosis to make the endosperm tissue which takes over the role of the nucellus in providing nutrients for the embryo.
