This document discusses seed dormancy and methods for breaking dormancy. It defines seed dormancy as a condition where seeds fail to germinate under favorable conditions. There are five main types of dormancy discussed: physical, physiological, morphological, morphophysiological, and combined dormancy. Common methods for breaking dormancy include stratification, scarification, and manipulating moisture, temperature, and light exposure.

2. NAME : YASIR AHMAD
C.NO : 64
SEMESTER : 2nd
DEPARTMENT : AGRONOMY
ASSIGMENT NO : 06
DEGREE : M.SC ( AGRONOMY)
SUBMITTED TO : PROF. DR. INAMULLAH

3. Seed
dormancy
• Seed dormancy refers to a condition in which
a seed fails to germinate under favorable
environmental conditions. In other words, it
is a period of arrested growth and
development of a seed even when all the
necessary conditions for germination are
present. Seed dormancy is an adaptive
mechanism that allows seeds to remain
viable and capable of germination for
extended periods, ensuring their survival in
unfavorable conditions.

5. Breaking seed Dormancy:
• To break primary dormancy and
promote germination in dormant
seeds, specific treatments or
conditions can be applied. Here are
some common methods used to break
primary dormancy:

6. 1. Stratification:
• Some seeds with primary dormancy require
a period of cold stratification. This involves
subjecting the seeds to a cold and moist
environment for a specific duration,
simulating winter conditions. Cold
stratification helps overcome the inhibitory
effects of ABA, allowing the embryo to
complete its development and germinate
when favorable conditions return.

7. 2. Scarification:
• Mechanical or chemical scarification
techniques can be employed to break primary
dormancy. By physically scratching or
chemically treating the seed coat, the barriers
that prevent water and gases from entering
the seed can be weakened or removed. This
allows for water imbibition, rehydration of
the embryo, and subsequent germination.

8. 3. Moisture and
Temperature
Manipulation:
• Adjusting the moisture and temperature
conditions can also influence the breaking of
primary dormancy. Seeds may require
specific levels of moisture or temperature for
dormancy release and germination. Adequate
moisture and suitable temperature conditions
activate physiological processes within the
seed that lead to the breakdown of dormancy
and the initiation of germination.

9. 4. Light
Exposure:
• Some seeds with primary dormancy require
exposure to light to break dormancy. Light
acts as a signal to stimulate germination.
Seeds that have a light requirement for
germination will not germinate when buried
too deep in the soil but will only germinate
when placed near or on the soil surface
where they can receive sufficient light.

10. TYPES OF
DORMANCY
1. Physical Dormancy (Seed Coat
Dormancy):
• Also known as hard seed coat dormancy,
this type of dormancy is caused by a hard or
impermeable seed coat that prevents water
and gases from entering the seed. The seed
coat acts as a physical barrier, protecting the
embryo from unfavorable environmental
conditions. Over time, natural weathering
processes or physical abrasion can break
down the seed coat, allowing water and
oxygen to penetrate and initiate
germination.

11. TYPES OF
DORMANCY
2. Physiological Dormancy:
• This type of dormancy is controlled by
physiological factors within the seed itself. It
occurs when the embryo is not fully developed
and requires specific conditions to trigger
germination. Physiological dormancy is often
influenced by hormones and growth inhibitors
present in the seed. For germination to occur,
the inhibitors must be degraded or diluted, and
hormone balances need to shift favorably.
Factors such as temperature fluctuations, light
exposure, and the presence of certain chemicals
can break physiological dormancy.

12. TYPES
OF DORMANCY
3. Morphological Dormancy (Embryo
Dormancy):
• Morphological dormancy occurs when the
embryo of the seed is not fully developed and
requires additional time or specific
environmental cues to complete its growth.
This type of dormancy is often found in
seeds of woody plants, such as trees and
shrubs. Environmental factors like cold
stratification (exposure to cold temperatures),
fire, or digestion by animals can scarify the
seed coat and stimulate embryo growth,
allowing germination to take place.

13. TYPES OF DORMANCY
4. Morphophysiological Dormancy:
Morphophysiological dormancy combines
both morphological and physiological
dormancy characteristics. Seeds with
morphophysiological dormancy have
underdeveloped embryos and may require
specific conditions such as exposure to light,
temperature fluctuations, or other
environmental triggers to break dormancy and
complete embryo growth.

14. TYPES OF DORMANCY
5. Combined Dormancy:
• Some seeds exhibit a combination of
different types of dormancy. For example, a
seed may have physical dormancy due to a
hard seed coat, as well as physiological
dormancy due to the presence of growth
inhibitors. In such cases, both the seed coat
barrier and the physiological factors need to
be overcome for successful germination.