The document discusses dormancy in plants, seeds, trees, bacteria, and viruses. It defines dormancy as a temporary suspension of growth and metabolic activity that helps conserve energy and is often associated with environmental conditions. It provides examples of different types of dormancy like physical dormancy caused by an impermeable seed coat, physiological dormancy preventing embryo growth until chemical changes, and morphological dormancy where the embryo is underdeveloped. Hard seed coats, temperature requirements, immature embryos, and growth inhibitory chemicals are mentioned as some causes of dormancy.

1. Ravi Yadav
Department of horticulture(Vegetable Science)
CoA,Tikamgarh(M.P)

2. Dormancy: is a period in an organism's life cycle when growth,
development, and (in animals) physical activity are temporarily
stopped.
This minimizes metabolic activity and therefore helps an
organism to conserve energy.
Dormancy tends to be closely associated with environmental
conditions.
Plant: Dormancy is a period of arrested plant growth.

3. Seed: When a mature and viable seed under a favorable
condition fails to germinate, it is said to be dormant.
Tree: Typically, temperate woody perennial plants require
chilling temperatures to overcome winter dormancy (rest).

4. Bacteria: Many bacteria can survive adverse conditions
such as temperature, desiccation,
and antibiotics by endospores, cysts, conidia or states of
reduced metabolic activity lacking specialized cellular
structures.
Virus: Dormancy in its rigid definition doesn't apply to
viruses, as they are not metabolically active.

5. During the developmental cycle of the plant, at some
phase certain structures like buds, tubers, seeds, go
through a period of temporary suspension of growth
activity, such a state is called dormancy.
It is derived Dormant word.
Dormant means sleeping or resting.
“Seed dormancy is defined as a state
in whichseeds are unable to germinate even under
Environmental conditions normally favorable for
germination.”

7. Exogenous dormancy
Physical dormancy
Mechanical dormancy
Chemical dormancy
Endogenous dormancy
Physiological dormancy
Morphological dormancy

8. Dormancy that is caused by an impermeable seed coat.
It is the result of impermeable layer that develops during
maturation and drying of the seed or fruit.
It prevents the seed from taking up water or gases.
As a result, the seed is prevented from germinating until
dormancy is broken.
Generally, physical dormancy is the result of one or more
palisade layers in the fruit or seed coat.

9. Mechanical dormancy:
Mechanical dormancy occurs when seed coats or other
coverings are too hard to allow the embryo to expand
during germination.
Chemical dormancy-
Presence of inhibitors within the seed (seed coat) can
cause dormancy.
E.g.: Coriander seed pericarp contains Coumarin
Paddy hull contain Abscisic acid

10. Physiological dormancy prevents embryo growth and seed
germination until chemical changes occur.
Photo dormancy: light sensitivity affects germination of
some seeds. These photoblastic seeds need a period of
darkness or light to germinate.
Thermo dormancy : seed sensitivity to heat or cold.
Some seeds germinate only at high temperature like
Amaranth.

11. In morphological dormancy, the embryo is underdeveloped
or undifferentiated.

12. Hard seed coat:hard and multilayered (Leguminaceae, Solonaceae).
Temperature: walnut, and Pinus. Such seeds needchilling (1 -5 ºC) for few weeks.
Immature Embryo:Caltha palustris.
growth inhibitory chemicals: Caffeic acid and Ferulic(tomato pulp)
Excessive Salts