The leafy portion
of a plant's embryo. The embryo is the part of the seed from
which a mature plant develops. It consists of a short root,
the radicle, and a short bud ,a
plumule, connected by a short shoot, the hypocotyl,
that bears one or more cotyledons. Because they form
within the seeds, cotyledons are known also as seed
leaves.Flowering plants,
called angiosperms,
have embryos within their seeds that form one or
two cotyledons, also often referred to as "seed
leaves". Those with one cotyledon are known
as monocotyledons or
monocots. Monocots include daylilies,
orchids, palms, bananas, pineapples, and corn. Most
have leaves with parallel veins and flower parts
in multiples of three. Angiosperms with two cotyledons
are called dicotyledons or
dicots. They produce leaves with a netlike pattern
of veins and flower parts in multiples of four or
five. Apples, cherries, beans, squashes, and tomatoes
are common dicots.
When seeds germinate,
the cotyledon/s may remain below the soil surface (known
as "hypogeous" germination), or emerge above
it (known as "epigeous" germination), depending
on the type of plant. For example, germinating daylily
seeds show hypogeous germination, the single cotyledon
remaining enclosed within the seed coat below ground.
An example of epigeous germination would be a bean
seed, where its two cotyledons are raised above ground
before the true leaves develop."
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