2. *
Some time the growth is suspended because of
the lack of favorable conditions in the
environment.
Such seeds will germinate if they are supplied
with water and suitable temperature.
In many other cases, even if they are not
provided with water etc.
This failure of seeds to germinate even under
favorable conditions is termed as Dormancy.
3. *
*The seed is called dormant and the phenomenon
is called dormancy.
*In majority of the cases, true dormancy helps the
seed to survive through an unfavorable season
e.g, very cold winter or a very hot summer
4. *
*Seed dormancy can be defined as the state or a
condition in which seeds are prevented from
germinating even under the favorable environmental
conditions.
*DORMANT:Not active
5. *
There are two types of seed dormancy.
*Seed coat(physical)Dormancy.
*Internal Dormancy.
6. *The dormancy of the seeds is regulated by
hormones or by temperature and restricted
oxygen uptake by hard seed-coat.
7. *
*Seed coats impermeable to water. ...
*Seeds coats impermeable to oxygen. ...
*Immaturity of the Embryo. ...
*Germination Inhibitors. ...
*Chilling or low temperature requirement. ...
*Light sensitive seeds.
*High temperature
8. *
*Dormancy helps seeds to remain alive in the soil for
several years and provides a continuous source of
new plants, even when all the mature plants of the
area have died down due to natural disasters.
9. *
* Exogenous Dormancy
Exogenous dormancy Exogenous dormancy is caused
by conditions outside the embryo.
*Endogenous Dormancy
Endogenous dormancy is caused by conditions within
the embryo itself
10. These are methods to overcome seed dormancy.
Artificial overcoming seed dormancy.
Treatment with hot water.
Hydraulic pressure of upto 2000kg for 5-20
mint.
11. *
Weakening of seed coat by mechanical abrasion or
injury.
Action of digestive enzymes present in alimentary
canals of birds and other animals which happens to
feed on their fruits.
Leaching of inhibitors present in seed coa.
Inactivation or oxidation of inhibitors by heat, cold
and light
12. *
*Hard seed coat.
*Mechanical resistance.
*Gas imperability.
*Dormancy due to specific light requirements.
*Dormancy due to germination inhibitors.
