Chapter 36 (Exam 2) Flashcards
In angiosperms, after the megasporocyte produces 4 megaspore, three of them die. How many mitotic divisions does this remaining megaspore undergo, and how many cells does it produce?
three divisions and 8 cells
Of the 8 cells that are within the ovule after the megaspore divides, two of them _____. This creates two haploid nuclei together in one cell, called _______ nuclei.
fuse; polar
What is the embryo sac?
The female gametophyte
In the embryo sac of angiosperms, after the polar nuclei are formed, 7 cells remain. Three of them move to the top and become __________ cells. Two _________ move to the opening at the bottom of the ovule. And one ______ cell goes in between them.
antipodal; synergids; egg
The pollen tube of angiosperms consists of which two cells?
the tube cell and generative cell
When the pollen tube arrives at the entrance of the ovule, the generative cell divides mitotically, producing two _______. One of the ___________ cells degenerates upon the pollen tube’s arrival.
sperms; synergid
One of the sperm fuses with the central cell with the ______________, and the other sperm fuses with the egg cell at the entrance of the ovule, forming a ____________.
polar nuclei; zygote
Self-pollination can occur in some plants, one example being peas. This can lead to __________, which reduces genetic diversity.
homozygosity
What mechanisms can plants have to prevent self-fertilization?
Physical separation of male and female gametes or genetic self-incompatibility
How is self-pollination physically prevented in dioecious plants?
The male and female plants are separate, so a plant cannot pollinate itself.
How is self-pollination physically prevented in monoecious species?
The male and female parts of the plant bloom at different times, making it impossible for a plant to pollinate itself.
Some plants prevent self-pollination by being self-incompatible. Describe what this entails.
The plant must have a way to recognize its own pollen. There is a specific gene that encodes proteins in the pollen and style that aid in the recognition process.
What is the name of the gene that encodes proteins in the pollen and style to prevent self-pollination?
the S locus gene
How does the S locus gene ensure the pollen is not from its own plant?
It can detect if the pollen carries an allele that matches the pistil.
In self-incompatible plants, what happens if the allele of the pollen matches the receiving pistil?
The pollen either fails to germinate or the pollen tube is prevented from growing in the style.
