Video Transcript
What is the specific term
scientists use to describe what happens after the pollen tube penetrates through the
opening in the ovule? (A) Double fertilization, (B)
fertilization, (C) germination, or (D) pollination.
This image displays a process that
occurs in flowering plants, which allows them to carry out sexual reproduction. Let’s take a closer look at what
needs to happen for sexual reproduction to occur and define some key terms along the
way.
Sexual reproduction involves the
fusion of a male sex cell and a female sex cell through a process called
fertilization. The male sex cells of flowering
plants are called sperm cells, and they’re contained within structures called pollen
grains. The female sex cells are called egg
cells, and each egg cell is found within a structure called an ovule in a flower’s
ovary. In this diagram, there is only one
ovule within the ovary, so only one egg cell.
Different flowering plant species
may have more than one ovule within the ovary and, therefore, multiple egg cells
too. For sexual reproduction to occur,
male sex cells must be able to access the female sex cell within the ovule so they
can fuse together in fertilization. To achieve this, first, a pollen
grain is deposited onto a part of the female reproductive organ of the flower called
the stigma. When this happens, the pollen grain
is said to germinate. This results in a structure called
a pollen tube growing out of the pollen grain and down the style, a structure which
separates the stigma from the ovary.
Two sperm cells travel down the
pollen tube, via the style, into the ovary. When the pollen tube penetrates the
opening in the ovule, the sperm cells can enter the ovule. Once they are within the ovule, one
of the two sperm cells can fertilize the egg cell. This forms a zygote. The zygote undergoes cell division
to form an embryo, which may eventually develop into a new individual plant. The second sperm cell fertilizes
another central cell that is already present in the ovule. The fertilized central cell forms a
food store for the new developing embryo. As there are two key fertilization
events that occur within the ovule of a flowering plant, this process is often
called double fertilization.
Now we know that there are two
fertilization events that occur in the ovule of a flowering plant when the pollen
tube penetrates it, we can answer this question. The most accurate term that can be
used to describe the process which occurs in the ovule at this point is (A), double
fertilization.
