Seed Chemistry, Viability and Germination

• The uniformity and speed of seedling emergence are important components of seed performance, thus directly affecting stand establishment.
• Most of our knowledge of the chemical composition of seeds concerns cultivated species, which comprise a large share of the food supply and provide many industrial raw materials.
• Seed viability tests assess whether a seed is alive, metabolically active, and possess enzymes capable of catalyzing metabolic reactions needed for germination and seedling growth.
• Aside from the normal chemical constituents found in a plant tissue, seeds contain extra amounts of chemical substances stored as food reserves to accommodate germination.
• These reserve foods are stored primarily as carbohydrates, fats (or oils), and proteins.
• Seeds contain other chemical substances, some of which play minor storage roles, but most of which serve as growth substances and metabolism controls.
• The chemical composition of seeds is determined by genetic factors and varies among different species and seed parts, but is influenced by environmental and cultural practices.
• Many environmental factors influence the chemical composition of seeds, and because of the interrelationships of these factors, it is sometimes difficult to determine the cause of variability.
• Carbohydrates are the major storage substance in seeds of most cultivated plants, with starch and hemicellulose being the major forms of carbohydrate storage in seeds.
• Other carbohydrates that occur in non-storage forms are pectins and mucilages.
• Lipids are the second major storage substance in seeds, with fatty acids, glycerol and other alcohols being the major forms of lipid storage in seeds.
• The great majority of seed proteins are metabolically inactive and serve merely as food reserves for use by the growing embryo during germination.
• Epigeal Germination is a type of germination where the cotyledons are raised above the ground where they continue to provide nutritive support to the growing points.
• Hypogeal Germination is a type of germination where the cotyledon or counter organs remain below the ground surface, while the plumule pushes upward and emerges above the ground surface.
• The sulphuric acid test is usually a non-enzymatic test.
• The tetrazolium test is often referred as a quick test since it can be completed within hours.
• The principle involved in the sulphuric acid test is to distinguish the differential coloration of live versus dead tissue when exposed to sulphuric acid.
• Stages of Seed Germination include Water Imbibition, Enzyme Activation, Initiation of Embryo Growth, Rupture of the Seed coat and Emergence of the Radicle, and Seedling Establishment.
• Seed maturity, water field capacity, aeration, temperature, and light are factors that affect Seed Germination.
• The accelerated aging test (AA) provides valuable information on storage and seedling field emergence potentials.
• The electrical conductivity test (EC) principle is that less vigorous or more deteriorated seeds show a lower speed of cell membrane repair during seed water uptake for germination and therefore release greater amounts of solutes to the external environment.
• Parts of the Growing Seed include Epicotyl, Hypocotyl, Radicle, and Plumule.
• Other Chemical Compounds found in Seeds include Tannins, Alkaloids, Glucosides, Phytin, Hormones (Gibberellins, Cytokinins, Inhibitors), and Vitamins (Thiamine, Ascorbic Acid).
• The cold test is considered the oldest vigor test method and probably the most popular used for seed vigor assessment in the United States.
• Seed vigor is the combination of characteristics that determine the potential for high performance after sowing.
• The uniformity and speed of seedling emergence are important components of seed performance, thus directly affecting stand establishment.
• Most of our knowledge of the chemical composition of seeds concerns cultivated species, which comprise a large share of the food supply and provide many industrial raw materials.
• Seed viability tests assess whether a seed is alive, metabolically active, and possess enzymes capable of catalyzing metabolic reactions needed for germination and seedling growth.
• Aside from the normal chemical constituents found in a plant tissue, seeds contain extra amounts of chemical substances stored as food reserves to accommodate germination.
• These reserve foods are stored primarily as carbohydrates, fats (or oils), and proteins.
• Seeds contain other chemical substances, some of which play minor storage roles, but most of which serve as growth substances and metabolism controls.
• The chemical composition of seeds is determined by genetic factors and varies among different species and seed parts, but is influenced by environmental and cultural practices.
• Many environmental factors influence the chemical composition of seeds, and because of the interrelationships of these factors, it is sometimes difficult to determine the cause of variability.
• Carbohydrates are the major storage substance in seeds of most cultivated plants, with starch and hemicellulose being the major forms of carbohydrate storage in seeds.
• Other carbohydrates that occur in non-storage forms are pectins and mucilages.
• Lipids are the second major storage substance in seeds, with fatty acids, glycerol and other alcohols being the major forms of lipid storage in seeds.
• The great majority of seed proteins are metabolically inactive and serve merely as food reserves for use by the growing embryo during germination.
• Stages of Seed Germination include Water Imbibition, Enzyme Activation, Initiation of Embryo Growth, Rupture of the Seed coat and Emergence of the Radicle, and Seedling Establishment.
• The sulphuric acid test is usually a non-enzymatic test.
• Hypogeal Germination is a type of germination where the cotyledon or counter organs remain below the ground surface, while the plumule pushes upward and emerges above the ground surface.