|Were do seeds come from? I know flowers form from
seeds but how do seeds form?
|Question Date: 2004-05-12|
A seed is a plant embryo, plus nutrient
feed the embryo, packaged in a protective shell.
Since it's an embryo, it's the product of sexual
Here's how it works.
When a seed
germinates, a plant grows out of it. It's only
partially true to say that flowers form from seeds
because, actually, the whole plant forms from the
seed. Even many non-flowering plants like pine
trees come from seeds. After the plant matures, it
reproduces. For flowering plants, that means they
make flowers to attract pollinators. Pollen is
delivered to flowers by bees, wind, or a number of
other "vectors." Sperm cells leave the pollen and
fertilize the eggs, which are found deep inside
the flower. The outer parts of the flower (the
parts we think are pretty) then die, but the inner
parts that contain the fertilized eggs develop
into fruit. All fruit scontain seeds (so tomatoes
and zucchinis are fruits, not vegetables).
The fruit's job is usually either to provide food
for the baby plant or to tempt an animal to eat the
fruit, spreading the seeds in the process. Once
the seeds are out of the fruit and into the ground,
they grow into new plants.
I hope that answers
I will here ignore the (potentially complicated)
process by which a pollen grain gets to an ovule;
it may be by wind or the pollen grain may travel
via a pollinating organism. In any case, when the
sperm reaches the ovule it fertilizes the egg to
form a zygote which develops into a young embryo.
As this proceeds, the embryo and its associated
nutritive cells enlarge, and so does the
As the embryo plus
nutritive reserves reach maturity, the integument
generally becomes hard and resistant and is then
refereed to as a seed coat. The whole structure
(embryo, food store & integument) is then referred
to as a seed, which may be dispersed by wind or
animals, thus spreading the genotype of the plant
over the surface of the Earth. The same
process, with certain variants, occurs in other
groups of plants that bear seeds (e.g., pine
trees, cycads, etc.)
Seed plants (not just flowering plants, but not
all plants) have organs called ovules where they
are going to produce seeds. The ovules are
fertilized by pollen, and then mature and grow to
become seeds. In a flowering plant, the ovules are
contained within the ovary, which is a bulbous
structure at the base of the flower. In a seed
plant that is not a flowering plant (such as a
conifer), the ovules are located inside of the
scales of the cones.
Consider the example of an
apple. The fruit is the ovary, which has grown and
enlarged after fertilization of the ovules (which
have become seeds). The flower, what is left of it
(the petals have all fallen off), is still on the
apple - on the end of the apple opposite the stem.
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