Seed dormancy refers to seeds not germinating during unsuitable conditions for seedling survival. There are three main types of dormancy - physical, physiological, and morphological. Dormancy prevents germination through impermeable seed coats, immature embryos, or germination inhibitors. Common methods to break dormancy include scarification, stratification, light exposure, and chemical treatments like gibberellic acid soaking. These treatments help prepare the seed and environment for successful germination.

1. SEED DORMANCY
BY-SAKET RANJAN
M.SC. PLANT BIOTECHNOLOGY
R.G.S.C (BHU)
EXAM ROLL NO.-20430PLB025

2. CONTENT
What is seed?
Seed dormancy
Types of seed dormancy
Cause of seed dormancy
Methods of breaking seed dormancy

3. What is seed?
 A seed is an embryonic plant enclosed in a protective outer covering.
 The fertilized, matured ovule of a flowering plant, containing an embryo
or rudimentary plant.
 Seed is material which is used For planting or regeneration purpose.
 Seed is a fertilized ripened ovule consisting of three main parts namely
seed coat , endosperm, and embryo which in due course give rise to a
new plant.
 Propagating material of healthy seedlings,tubers, rhizome, bulbs ,root,
cutting,setts,all type of grafts and vegetatively propagating materials
used for production purpose.

5. SEED DORMANCY
 Seed dormancy is an evolutionary adaptation that prevents seeds
from germinating during unsuitable ecological conditions that
would typically lead to a low probability of seedling survival.
 True dormancy or innate dormancy is caused by conditions within
the seed that prevent germination under normally ideal
conditions.
 Seed dormancy is divided into two major categories based on
what part of the seed produces dormancy:-exogenous and
endogenous
 There are three types of dormancy based on their mode of
action: physical, physiological and morphological.

6. TYPES OF SEED DORMANCY
1. Primary dormancy:-when seed fails to germinate due to
internal causess even if favourable environmental condition
are provided for germination. E.g-potato
2. Secondary dormancy:-seeds of some plants may
germinates immediately in favourable environmental
condition but dormancy can be induced in this seeds if
provided adverse conditions. E.g:-white mustard
3. Special dormancy:-Seeds of some plants species germinates
but primary root fails to develop, epicotyl growth is
stopped.

7. Causes of seed dormancy
1. Impermeability of seed coat to water. E.g- plants of family
leguminaceae,solanaceae,chenopodiaceae,convolvoaceae
2. Seed coat impermeable tooxygen. E.g- Xanthium.
3. Seed coat restricting mechanically the growth of embryo .E.g:-Mustard and
amaranths
4. Immaturity of embryos. E.g:- Datura ,peach etc.
5. Germination inhibitors. E.g:- tomato sap, circulic acid in rice hull
6. Light requirement. E.g:- carrot,lettuce needs light for dormancy while Datura not
needs light for dormancy
7. Temperature requirement. E.g:-apple ,pear ,peach need low temperature for
dormancy.

8. Methods for breaking dormancy
 SCARIFICATION:- (mechanical treatment) Practice of breaking the hard seed coat by
mechanical treatment.
a)Chilling:- seeds are placed in temperature between 5 to 10 degree Celsius for 7days
for germination. E.g-cabbage, cauliflower, sunflower
b)Pre-drying:- seeds are dried below 40 degree Celsius for 7days. E.g-maize, lettuce
c)pre-washing:- removal of germination inhibitors by soaking & washing seed in water.
E.g:-sugarbeet
d)pre-soaking:- seeds are soaked in warm water for some period to enhance imbibition
process in seed. E.g-chilli, subabul
e) Rubbing or puncturing seed coat:- seed are either rubbed against rough surface or
punctured with pointed needle. E.g-Coriander, castor
f) Application of pressure to seeds:- Germination increase is seed in some plants when
hydraulic pressure is applied on it. E.g- Medicago sativa.

9. Continued....
 STRATIFICATION:- In some seeds after ripening ,low temperature and moisture conditions
required in artificial stratification .Seed layer altered with layers of moist sand or appropriate
material to store at low temperature. E.g- Mustard & ground nut
 EXPOSURE OF SEEDS TO LIGHT:- It also helps to break the dormancy & increase the germination.
 CHEMICAL TREATMENT:-
a)pottasium nitrate treatment:- 2% solution of KNo3 is mixed in seeds .
e.g- Rice, tomato, chilli
b) Gibberellic acid treatment:- seeds may be moistened with 500 ppm solution of GA.
e.g:- wheat ,oat
c)Thio-urea treatment:- Potato tubers are dipped in thio-urea solution (1%) for 1 hour when fresh
harvested produce is to be used as seed material.