Download Germination


Germination
Biology 104
Authors:
Lucy
Morgan
Becka
Carrie
What is germination?
 Germinate- To begin to grow or develop, to develop
into a plant or individual as a seed spore or bulb. To
put forth shoots; sprout; pullulate.
 Pullulate- to send forth sprouts, buds or to sprout.
Dictionary.com
What conditions required for
germination?
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Period of Dormancy
•
Germination begins with imbibition, as the seed
absorbs water to make the seed coat permeable.
•
Imbibition is when a seed absorbs enough water to
soften the seed coat and break dormancy. This
allows germination to begin.
•
Seeds need moisture, proper temperature,
darkness and light.
Biology: Life on Earth
Dictionary.com
Example:
Arabidopsis Germination Requirements
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Arabidopsis plants are winter annuals, which means the seeds
germinate in fall, survive winter, flower in spring and seeds are
dormant in the summer.
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Dormancy can be broken by a imbibing seeds at 4 degrees Celsius for
2-4 days.
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For germination seeds must have a high humidity, about 25-75%
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The photoperiod must also be around 8 hrs of light and 16 hrs of dark
Arabidopsis: A Laboratory Manuel
Importance of Dormancy Period
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Often, seeds require a preceding period of dormancy.
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Dormant- inactive, latent, but capable of being activated, suspension of
metabolic process.
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Seeds of many temperature-climate angiosperms will germinate only
after a prolonged period of cold. An inhibitor within the seed usually
abscisic acid, or ABA, is gradually broken down at a low temperature until
finally there is not enough to prevent germination when other conditions
become favorable.
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This is an obvious mechanism of survival, preventing seeds from
germinating during an unseasonably warm spell in the autumn.
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ABA- plant hormone that maintains a water balance of plants, prevents
seed embryos from germinating, induces the dormancy of seeds.
Biology: Life on Earth
Wikipedia.com
Lovetoknowgardener.com
Why don’t all seeds germinate at the
same rate?
 Seeds require different ideal germination conditions
 Time delays between ideal conditions cause variations
in germination rates.
 Growing days- a certain number of days when growing
conditions are favorable.
 If the plant does not get enough growing days it will die
before flowering.
Wikipedia.com
Consequences of germinating too soon
or too late.
 If a seed germinates too early it might exhaust its
food reserves before its roots are fully developed
to support the plant.
 Environmental conditions that are suitable for
seedling growth might not coincide with seed
maturity. Example: if a seed germinates in late
summer then it will have to face the cold of
winter.
Wikipedia.com
Biology: Life on Earth
Common Causes of Germination Failure
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Soil: being too heavy, wet or cold
 Drying out: slow seeds not having long enough to
come up. Reasons of burning out are due to placing
seeds in full sun, or outdoor conditions too quickly.
Pests eating the seeds
 Dormant seeds not receiving proper pre-treatment,
poor air circulation, and over-watering.
Lovetoknowgardner.com
Why do germinated seeds produce roots
first? Why not leaves first?
 The part of the plant that emerges from the seed
first is the embryonic or primary root. This allows
the seedling to become anchored in the ground,
and start absorbing water.
 After the roots absorb water, the embryonic shoot
emerges from the seed.
 The shoot then grows and begins to
photosynthesize
Biology: Life on Earth
Where does the energy and material
come from to create the growing root?
 The seed has energy and raw material stored in the
cotyledons or the endosperm
 This energy supports the growth of the plant until it
is able to photosynthesize.
Biology: Life on Earth
Sources:
 Dictionary.com
 Wikipedia.com
 Biology: Life on Earth
 Lovetoknowgardner.com
 Arabidopsis: A Laboratory Manuel