plant Nutrition final seed dormancy

35問 • 1年前

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as any phase in the life cycle of a plant in which active growth is temporarily suspended.

dormancy

Is a condition where seeds will not germinate even when the environmental conditions (water, temperature and aeration) are permissive for germination (Copeland and McDonald, 2001)

seed dormancy

is defined as a state in which seeds are unable to germinate even under environmental conditions normally favorable for germination

Seed dormancy

Types mode in seed dormancy

Mode of seed origin Mode of seed structure Mode of action

Mode of seed origin

Primary & Secondary Dormancy

Mode of seed structure

Embryo Induced & Coat Induced Dormancy

Mode of action

Exogenous & Endogenous dormancy

this is an inherent dormancy status of a maturing seed when its fully developed on the parent plant. This is when the seed is released from the mother plant in a dormant state

Primary dormancy

this is an inherent dormancy status of a maturing seed when its fully developed on the parent plant. This is when the seed is released from the mother plant in a dormant state

Primary dormancy

This is when the seed released from a parent plant becomes dormant as a result of environmental conditions.

Secondary dormancy

Due to internal causes even if all external environmental conditions are duly present. Ex:Hormonal factor (ABA-GA imbalance), Genetic factors

Primary Dormancy:

When dormancy caused due to external factors like absence of sunlight, CO2, very high or low temperature. Ex: Nicotiana attenuata only germinate if there is presence of smoke.

Secondary Dormancy:

Types of mode of origin

primary dormancy secondary dormancy

Seed dormancy can be categorized into two main groups based on the parts of the seed where the dormancy affects and control.

Mode of seed structure:

Type of mode of seed structure

embryo induced dormancy coat induced dormancy

the dormancy is within the embryo itself and usually caused by undeveloped or complete dormant embryo

Embryo induced dormancy

: This is the dormancy which resides within the structure (seed coat) enclosing the embryo and caused by extreme hardness of the seed coat.

Coat induced dormancy

Classification of Exogenous dormancy

➤ Physical dormancy ➤ Physiological dormancy ➤ Mechanical dormancy

Classification of Endogenous dormancy

➤ Morphological dormancy ➤ Chemical dormancy ➤Combined dormancy

occurs when seed coats or other coverings are too hard to allow the embryo to expand during germination.

Mechanical dormancy

Presence of inhibitors within the seed (seed coat) can cause dormancy.

Chemical dormancy

prevents embryo growth and seed germination until chemical changes occur

Physiological dormancy

Types of physiological dormancy

photo dormancy thermo dormancy

light sensitivity affects germination of some seeds. These photoblastic seeds need a period of darkness or light to germinate

Photo dormancy

seed sensitivity to heat or cold. Some seeds germinate only at high temperature. like Amaranth.

Thermo dormancy

the embryo is underdeveloped or undifferentiated.

morphological dormancy

These seeds have both morphological and physiological dormancy.

Combined dormancy

prevents embryo growth and seed germination until chemical changes occur

Physiological dormancy

In this class, seeds have embryos that are underdeveloped (in size), but differentiated (e.g., into cotyledons and hypocotyls radical) as well as a physiological component to their dormancy.

Morpho-physiological dormancy:

TYPES OF DORMANCY According to wareing (1969) the dormancy may be two types

Imposed dormancy or quiescence :Innate dormancy or rest:

The dormancy due to unfavourable environmental conditions is called imposed dormancy or quiescence.

Imposed dormancy or quiescence:

The dormancy due to conditions within the dormant plant or organ is called innate dormancy or rest.

Innate dormancy or rest:

TYPES OF SEED DORMANCY ◆Crocker (1916) divided seed dormancy into two types:

Seed coat induced dormancy: Embryo induced dormancy:

The dormancy of seeds due to extreme hardness of seed coat is called seed coat induced dormancy.

seed coat dormancy

The dormancy of seeds due to rudimentary or complete dormant embryo is called embryc induced dormancy.

Embryo induced dormancy:

plant diseases symptoms

Ezekiel Emano · 47問 · 1年前

plant diseases symptoms