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True dormancy or inherent (or innate) dormancy is caused by conditions within the seed that prevent germination even if the conditions are favorable. [7] Imposed dormancy is caused by the external conditions that remain unsuitable for germination [8] Seed dormancy can be divided into two major categories based on what part of the seed produces dormancy: exogenous and endogenous. [9]
Dormancy should not be confused with seed coat dormancy, external dormancy, or hardheadedness, which is caused by the presence of a hard seed covering or seed coat that prevents water and oxygen from reaching and activating the embryo. It is a physical barrier to germination, not a true form of dormancy (Quinliven, 1971; Quinliven and Nichol ...
Exogenous dormancy is caused by conditions outside the embryo, including: Physical dormancy or hard seed coats occurs when seeds are impermeable to water. At dormancy break, a specialized structure, the 'water gap', is disrupted in response to environmental cues, especially temperature, so water can enter the seed and germination can occur.
The exogenous dormancy is controlled by environmental factors such as temperature or nutrient availability. The endogenous or constitutive dormancy depends on characteristics of the spore itself; for example, metabolic features. In this type of dormancy, germination may be prevented even if the environmental conditions favor growth.
Abscisic acid (ABA or abscisin II [5]) is a plant hormone.ABA functions in many plant developmental processes, including seed and bud dormancy, the control of organ size and stomatal closure.
Endogenous hormone levels are influenced by plant age, cold hardiness, dormancy, and other metabolic conditions; photoperiod, drought, temperature, and other external environmental conditions; and exogenous sources of PGRs, e.g., externally applied and of rhizospheric origin.
Dormancy is a stage in cancer progression where the cells cease dividing but survive in a quiescent state while waiting for appropriate environmental conditions to ...
Gibberellic acid is sometimes used in laboratory and greenhouse settings to trigger germination in seeds that would otherwise remain dormant. [3] It is also widely used in the grape-growing industry as a hormone to induce the production of larger bunches and bigger grapes, especially Thompson seedless grapes.