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Seed dormancy

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**Types of Seed Dormancy:**
– True dormancy caused by internal seed conditions
– Imposed dormancy due to external factors
– Exogenous and endogenous dormancy
– Inherent types: physical, physiological, and morphological
– Classification schemes vary due to overlapping reasons

**Exogenous Dormancy:**
– External conditions cause this type
– Divided into physical, mechanical, and chemical dormancy
– Physical dormancy: impermeable seed coats
– Mechanical dormancy: hard seed coats hindering embryo expansion
– Chemical dormancy: growth regulators in coverings

**Endogenous Dormancy:**
– Caused by conditions within the embryo
– Divided into physiological, morphological, and combined dormancy
– Physiological dormancy: chemical changes needed for germination
– Morphological dormancy: underdeveloped embryos
– Combined dormancy: mix of physiological and morphological aspects

**Secondary Dormancy:**
– Occurs in non-dormant or post-dormant seeds
– Triggered by unfavorable post-dispersion conditions
– Mechanisms involve changes in receptor sensitivity
– Loss of sensitivity in plasma membrane receptors may play a role

**Seed Dormancy Research and Publications:**
– Authors like Nadarajan, Benson, Li, Baskin, Sharma, Boesewinkel, and Nandi
– Key studies on seed structure, anatomy, and dormancy mechanisms
– Further reading recommendations like “The Triumph of Seeds”
– Texts and resources for exploring seed dormancy in-depth

Seed dormancy (Wikipedia)

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. Dormant seeds do not germinate in a specified period of time under a combination of environmental factors that are normally conducive to the germination of non-dormant seeds.

An important function of seed dormancy is delayed germination, which allows dispersal and prevents simultaneous germination of all seeds. The staggering of germination safeguards some seeds and seedlings from suffering damage or death from short periods of bad weather or from transient herbivores; it also allows some seeds to germinate when competition from other plants for light and water might be less intense. Another form of delayed seed germination is seed quiescence, which is different from true seed dormancy and occurs when a seed fails to germinate because the external environmental conditions are too dry or warm or cold for germination.

Many species of plants have seeds that delay germination for many months or years, and some seeds can remain in the soil seed bank for more than 50 years before germination. Seed dormancy is especially adaptive in fire-prone ecosystems. Some seeds have a very long viability period, and the oldest documented germinating seed was nearly 2000 years old based on radiocarbon dating.

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