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Lecture 4

BIOL-1507EL Lecture 4: Seed dormancy and Seed Germination in Angiosperms

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Nasserulla Sabah

Lecture 4 Seed dormancy and germination - The growth of the embryo is usually arrested while the seed matures and is dispersed - Resumption of the growth, or germination is dependant on many factors, among the external factors; 1) water (most important), 2) oxygen, 3) temperature most mature seed are extremely dry, normally containing only 5% - 20% of their total dry weight - Thus germination is not possible until the seed imbibes the water required for metabolic activity - During the early stages of germination, respiration may be entirely anaerobic, but as soon as the seed coat ruptured, the seed switches to aerobic respiration - Many seeds will germinate over a wide range of temperatures; they usually will not germinate either below or above a certain temperature - - the minimum temperature for most species: 0 – 5 c o - - the max  45 – 48 c o o - - the optimum temperature: 25 – 30 c in some cases even if the external conditions are favourable for seed germination, some seed will fail to germinate, such seeds are said to be dormant. - The two most common causes for seed dormancy, 1) the impermeability of the seed coat to water and some time to oxygen 2) the physiological immaturity of the embryo, some physiological immature seeds must undergo a complex series of enzymatic and biochemical changes before they will germinate. - Collectively thes
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