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Development and structure of seeds:
We know that after fertilization in the female
gametophyte, Zygote divides repeatedly by mitosis
and develops into an embryo
...
The formation of seed completes the process
of sexual reproduction in seed plants
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Angiosperm seeds consists of three distinct parts:
(1) the embryo formed from zygote,(2) the
endosperm tissue formed from endosperm nucleus,
and (3) the seed coat which develops from the wall
of ovule (integument)
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It may be a paperthin layer (e
...
peanut) or thick and hard (e
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Seed coat protects embryo from

Mechanical injury and from drying out
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It is where the seed
is attached to ovary wall (fruit)
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This is the same opening
through which the pollen tube entered ovule
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Embryo is actually an immature plant
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The radicles of embryo develop into new
root while the plumule develops into new shoot
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The embryonic
stem below the point of attachment is hypocotyl
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In
angiosperms, the stored food is derived from the
angiosperm tissue
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In many seeds, the food of the
endosperm is absorbed and stored by cotyledons
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Germination of Seeds:
For the germination of seeds, they must arrive at a
suitable location and be there at a time favorable
for germination and growth
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During
germination, embryo soaks up water which causes
it to swell, splitting the seed coat
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It grows rapidly and absorbs water and
nutrients from soil
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|Most seeds go through a period, during which
there is no growth
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Dormant seeds are ripe
seeds but do not germinate
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On the basis of the elongation of hypocotyl and
epicotyl, there are two types of germination (in
below fig)
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Beans, cotton papaya are the

examples of seeds that germinate this way
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In these types of germination, the
cotyledons stay underground
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Conditions for Seeds Germination:
Seeds germination depends on both internal and
external conditions
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The most important external conditions
include water, oxygen and favorable temperatures
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Water (moisture): Seeds of most plants have low
water content, and germination cannot occur until
seed coat or other tissues have imbided (take in)
water
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Oxygen: oxygen is essential for the respiration in
the cells of embryo
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The
optimum temperature for the germination of the
seeds of most plants ranges from 25-30C
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Identify and draw the component of the seeds
of pea and gram
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Perform experiment to investigate the
necessary conditions for seed germination

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