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Fruits  Fruit development
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DEVELOPMENT OF FRUIT
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The structure of
a fruit often facilitates the dispersal
of its seeds. The “wings”
of the maple, elm, and ailanthus fruits
and the “parachutes” of
the dandelion and the thistle are
blown by the wind; burdock, cocklebur,
and carrot fruits have barbs or hooks
that cling to fur and clothing; and
the buoyant coconut may float thousands
of miles from its parent tree. Some
fruits (e.g., witch hazel and violet)
explode at maturity, scattering their
seeds. A common method of dispersion
is through the feces of animals that
eat fleshy fruits containing seeds
covered by indigestible coats.
After the part of the flower is pollinated,
pollen grains attempt to travel into
the ovary by creating a path called
"pollen tube." The pollen
tube does not directly reach the ovary
in a straight line. It travels near
the skin of the style and curls to
the bottom of the ovary, then near
the receptacle, it breaks through
the ovule and reaches the ovum to
fertilize it. After being fertilized,
the ovary starts to swell and becomes
a fruit.
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With multi-seeded fruits, multiple
grains of pollen are necessary for
syngamy with each ovule. The process
is easy to visualize if one looks
at maize silk, which is the female
flower of corn. Pollen from the tassel
(the male flower) falls on the sticky
external portion of the silk, then
pollen tubes grow down the silk to
the attached ovule. The dried silk
remains inside the husk of the ear
as the seeds mature, so one can carefully
remove the husk to show the floral
structures. The development
of the flesh of the fruit is proportional
to the percentage of fertilized ovules. |
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Special fruits for this week
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.jpg "Strawberries have seeds outside them")
