seed physiology

this is seed physiology presentation

2. SEED GERMINATION:
Definition:
Germination is the process in
which a seed or spore emerges
from a period of dormancy.
The most common
example of germination
is the sprouting of a
seedling from a seed of
an angiosperm or
gymnosperm.

3. A SEED IS AN EMBRYO
PLANT AND CONTAINS
WITHIN ITSELF VIRTUALLY
ALL THE MATERIALS AND
ENERGY TO START OFF A
NEW PLANT.
THE SEED OF A HIGHER PLANT
IS A SMALL PACKAGE
PRODUCED IN A FRUIT OR
CONE AFTER THE UNION OF
MALE AND FEMALE SEX CELLS.

4. GERMINATION RATE:- IN
AGRICULTURE AND GARDENING,
THE GERMINATION RATE
DESCRIBES HOW MANY SEEDS OF
A PARTICULAR PLANT SPECIES,
VARIETY OR SEED LOT ARE
LIKELY TO GERMINATE. IT IS
USUALLY EXPRESSED AS A
PERCENTAGE, E.G., AN 85%
GERMINATION RATE INDICATES
THAT ABOUT 85 OUT OF 100 SEEDS
WILL PROBABLY GERMINATE
UNDER PROPER CONDITIONS. THE
GERMINATION RATE IS USEFUL
FOR CALCULATING THE SEED
REQUIREMENTS FOR A GIVEN
AREA OR DESIRED NUMBER OF
PLANTS.

5. FACTOR AFFECTING OF
SEED GERMINATION:-
(A) EXTERNAL FACTOR
(B) INTERNAL FACTOR

6. (A) EXTERNAL
FACTOR
Also known as environment factor.
Most important factor affecting
germination of seed are following:
3.Water
4.Temperature
5.Aeration
6.Light

7. WATER:
WATER IS REQUIRED FOR
GERMINATION. MATURE SEEDS ARE
OFTEN EXTREMELY DRY AND NEED TO
TAKE IN SIGNIFICANT AMOUNTS OF
WATER, RELATIVE TO THE DRY WEIGHT
OF THE SEED, BEFORE CELLULAR
METABOLISM AND GROWTH CAN
RESUME. MOST SEEDS NEED ENOUGH
WATER TO MOISTEN THE SEEDS BUT
NOT ENOUGH TO SOAK THEM.

8. THE UPTAKE OF WATER BY
SEEDS IS CALLED IMBIBITION,
WHICH LEADS TO THE SWELLING
AND THE BREAKING OF THE SEED
COAT. WHEN SEEDS ARE FORMED,
MOST PLANTS STORE A FOOD
RESERVE WITH THE SEED, SUCH
AS STARCH, PROTEINS, OR OILS.
THIS FOOD RESERVE PROVIDES
NOURISHMENT TO THE GROWING
EMBRYO. WHEN THE SEED
IMBIBES WATER, HYDROLYTIC
ENZYMES ARE ACTIVATED WHICH
BREAK DOWN THESE STORED
FOOD RESOURCES INTO
METABOLICALLY USEFUL
CHEMICALS.

9. AFTER THE SEEDLING EMERGES
FROM THE SEED COAT AND
STARTS GROWING ROOTS AND
LEAVES, THE SEEDLING'S FOOD
RESERVES ARE TYPICALLY
EXHAUSTED; AT THIS POINT
PHOTOSYNTHESIS PROVIDES
THE ENERGY NEEDED FOR
CONTINUED GROWTH AND THE
SEEDLING NOW REQUIRES A
CONTINUOUS SUPPLY OF WATER,
NUTRIENTS, AND LIGHT.

10. OXYGEN:
Oxygen is required by the germinating seed
for metabolism. Oxygen is used in aerobic
respiration, the main source of the seedling's
energy until it grows leaves.
Oxygen found in soil pores.

11. SOME SEEDS HAVE
IMPERMEABLE SEED COATS
THAT PREVENT OXYGEN FROM
ENTERING THE SEED,
CAUSING A TYPE OF PHYSICAL
DORMANCY WHICH IS BROKEN
WHEN THE SEED COAT IS
WORN AWAY ENOUGH TO
ALLOW GAS EXCHANGE AND
WATER UPTAKE FROM THE
ENVIRONMENT.

12. TEMPERATURE :
Temperature affects cellular
metabolic and growth rates.
Seeds from different species
and even seeds from the same
plant germinate over a wide
range of temperatures. Seeds
often have a temperature
range within which they will
germinate, and they will not do
so above or below this range.

13. MANY SEEDS GERMINATE AT
TEMPERATURES SLIGHTLY ABOVE
ROOM-TEMPERATURE 60-75
0
F
(16-24 C), WHILE OTHERS
GERMINATE JUST ABOVE
FREEZING AND OTHERS
GERMINATE ONLY IN RESPONSE
TO ALTERNATIONS IN
TEMPERATURE BETWEEN WARM
AND COOL. SOME SEEDS
GERMINATE WHEN THE SOIL IS
COOL 28-40
0
F (-2 - 4
0
C), AND SOME
WHEN THE SOIL IS WARM 76-90
0
F
(24-32
0
C). SOME SEEDS REQUIRE
EXPOSURE TO COLD
TEMPERATURES
(VERNALIZATION) TO BREAK
DORMANCY.

14. SEEDS IN A DORMANT STATE WILL NOT
GERMINATE EVEN IF CONDITIONS ARE
FAVORABLE. SEEDS THAT ARE
DEPENDENT ON TEMPERATURE TO
END DORMANCY HAVE A TYPE OF
PHYSIOLOGICAL DORMANCY. FOR
EXAMPLE, SEEDS REQUIRING THE
COLD OF WINTER ARE INHIBITED
FROM GERMINATING UNTIL THEY
TAKE IN WATER IN THE FALL AND
EXPERIENCE COOLER
TEMPERATURES. FOUR DEGREES C IS
COOL ENOUGH TO END DORMANCY
FOR MOST COOL DORMANT SEEDS,
BUT SOME GROUPS, ESPECIALLY
WITHIN THE FAMILY RANUNCULACEAE
AND OTHERS, NEED CONDITIONS
COOLER THAN -5
0
C.

15. LIGHT OR DARKNESS:
Light or darkness can be an
environmental trigger for
germination and is a type of
physiological dormancy. Most seeds
are not affected by light or darkness,
but many seeds, including species
found in forest settings, will not
germinate until an opening in the
canopy allows sufficient light for
growth of the seedling.

16. ENVIRONMENT CONTROL ON
GERMINATION:
we are use many method of
environment control as following:
Temperature: Most seeds germinate
best at warm (70°F) temperatures.
Temperatures used in the catalog are:
Cold (34 - 45°F), Cool (50 - 65°F), Warm
(65 - 80°F) and Very Warm (80 - 100°F).

17. Light/Dark: Some seeds need light to
germinate; others need darkness, and light
prevents sprouting. If light is required,
sow on the surface; if darkness is needed,
cover seed well.
Carbon dioxide: CO
2
reduces the
percentage of germination. However, CO
2
high concentration, promotes germination
in Xanthium, Lactuca and Trifolium.

18. Gibberellic Acid-3 (Ga-3): GA-3 is a
naturally occurring plant growth
regulator. Presoaking seeds in GA-3 will
often cause rapid germination of many
highly dormant.
Hot Water Soak: The seeds are placed
in a cup and not quite boiling (200°F)
water is poured on them and allowed to
cool & the seeds to swell. water for 10
seconds to 3 minutes.

19. Dry Heat: The seeds are baked dry in
an oven at 140° to 220°F for 4 - 10 hours,
or are microwaved for 30 seconds to 4
minutes.
Warm Moist Treatment: Many seeds
need 1- 4 months of warm moist
treatment, followed by cold treatment to
sprout. In some, the root sprouts during
the warm period, but the shoot does not
sprout until after a cold period

20. Smoke Treatment: Smoke treatment
often helps germination of plants from
fire-prone environments, particularly
Mediterranean-climate plants .
Hard Seeds-Chipping: Hard seed coats
which prevent moisture being absorbed
by the seed. All that is needed is for the
outer surface to be scratched or abraided
to allow water to pass through.

21. Hard Seeds-Soaking: Soaking is
beneficial in two ways; it can soften a
hard seed coat and also leach out any
chemical inhibitors in the seed which may
prevent germination. 24 hours in water
which starts off hand hot is usually
sufficient.
Stratification (cold treatment):
artificially stimulated by placing the
moistened seed in a refrigerator for a
certain period of time (usually 3- 5 weeks
at around 41
0
F).