4. Types of dormancy
1. Seed Dormancy
2. Dormancy due to rudimentry
embryo
3. Dormancy due to internal factors
4. Dormancy due to chemical
inhibitors
5. Double dormancy
5. 1. Seed dormancy:
• When viable seed faced to germinate even
through the proper condition is given. This
phase is known as seed dormancy. It is also
known as resting period of seed.
2.Dormancy due to rudimantary emryos:
Some plant shed their fruit before the
embryo within the
seed has attained the maturity stage to
germinate. Such embryos require several
weeks to several months after harvest to
attain its fully maturity so that it germinate .
Eg: Ilex spp, Pinus spp,plams, orchids etc.
6. 3.Dormancy due to the internal factors:
• Due to the physiologically dormant embryos. In
this case, the dormant embryos do not resume
active growth eventhrough all environmental
conditions are favourable, unless the seeds are
subject to moist, chilling treatment, treatment.
During this process, the level of endgenous growth
growth promoting substance (Eg: gibberelines,
cytokininis) increases the level of growth inhibiting
hormones (eg: abscissic acid) decreases, thus
removeing the block and promoting germination.
Eg: Freshly harvested seeds of apple,pear peaches,
apricot, rose and grapes do not germinate due to
above factor
7. 4. Dormancy due to chemical
inhibitors:
In certain species, specific
chemical substance that prevent
germination occurs in the seed
coats endosperms or the embryo.
These reduced or eliminated by
leaching with water or absorption
by soil.
8. 5. Double dormancy:
Seeds of some species
(eg: Cercis occidentals)
exhibit seed coat
dormancy and embryo
dormancy.
9. Method of breaking
dormancy
1. Scarification:
The method of breaking of
seeds caused by hard seed coat
which become impermeable to
water and gases etc
Scarification is done by treating
seeds with concentrated HCL or
H2so4 for a specificed followed
by through washing. Eg pulses,
seeds of forest trees
10. 2. Scarification
• Dormancy is seeds of many
wood herbaceous species is
broken when hydrated seed
exposed to relatively low
temperature (0 degree to 20
degree) for 3 to 7 days
11. 3. High temperature
treatment:
• Dry heating of seed at 40
degree to 55 degree celcious
temperature for several days
have been found effecting in
breaking dormancy in paddy
and groundnut.
12. 4. Light treatment:
• Some seed do not
germinate in dark thus it
provide periodic exposure
light is essential. Eg: Lettuse
required red light or white
light for it's germination.
14. 6. Hot water:
It is also effecting method for
breaking dormancy.
The seeds are soaked in water
of 80 degree for 1 to 5 minute
to break it's dormancy or seed
coat depending upon types of
seed example legme seed.
15. 7.Dry storage:
• The embryo of seeds of certain
species is not fully development
even at harvestable maturity
stage and requires soome more
time after harvest (after ripening
period) for full development of
embryo.Dry storage of such seeds
for few days will break dormancy
and promote germination.
16. 8. Chemical treatment:
• Various chemicals and
hormones, gibberellines,
cytokinins, ethylene, KNO3, HNO3,
cyanide etc have been found to
break seed dormancy in different
species. The concentration of the
chemicals and mode of
treatment varies in seeds.
