Handbook of Plant and Crop Physiology

64 CHONG ET AL.

TABLE 1

Types of Seed Dormancy, Causal Factors, and Treatment Strategies

Types of dormancy

Cause

Treatment strategies

Comments

Seed coverings include capsules, hulls, pits

or shells, and mucilaginous or fleshy partsof fruits that may become hardened.

In nature or outdoor sowing, seed is

“scarified” by alternate freezing andthawing, action of soil microbes; also bypassage through intestines of animals or byfire.

Inhibitors include abscissic acid, phenols,

and coumarins. In nature leaching accessdue to sufficient soil moisture and rainfall.

“After-ripening” is defined as a period of dry

storage required by some seeds to losedormancy. This type of dormancy occursin freshly harvested seeds of manyherbaceous and some trees species. It oftendisappears with normal harvesting andhandling of the seeds.

Soften, rupture, or remove; mechanical

abrasion; alternate freezing andthawing.

Rupture or remove; warm or cold

treatment.

Remove seed coverings and/or leach with

water.

A period of warm temperature usually

favors embryo development;sometimes cold treatment, alternatingwarm and cold or gibberellic acid;excise embryo and germinateaseptically.

A short period of dry storage; sometimes

short periods of chilling; alternatingtemperatures, potassium nitrate, orgibberellic acid.

Induced by seed-related factors although

germination environment may befavorable.

Regulated by factors outside the embryo,

usually seed coat and other externalcovering.

Seed coat impervious to water or restricts

aeration.

Hard seed covering constrains the

embryo.

Seed coverings release chemical

inhibitors or prevent leaching ofinhibitors.

Regulated by internal and physiological

factors within the embryo.

Rudimentary or immature embryo.Semipermeable inner seed coat or active

membranes; restricted gaseousexchange and inhibitor movement;possible excess of abscissic acid.

Lack of “after-ripening.”

A. Primary1. Exogenous

Physical MechanicalChemical

2. Endogenous

Morphological PhysiologicalNondeep (transitory)