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germination,in a seed, process by which the plant embryo within the seedseed,
fertilized and ripened ovule, consisting of the plant embryo, varying amounts of stored food material, and a protective outer seed coat. Seeds are frequently confused with the fruit enclosing them in flowering plants, especially in grains and nuts.
..... Click the link for more information. resumes growth after a period of dormancy and the seedling emerges. The length of dormancy varies; the seed of some plants (e.g., most grasses and many tropical plants) can sprout almost immediately, but many seeds require a resting stage before they are able to germinate. The viability of seeds (their capacity to sprout) ranges from a few weeks (orchids) to up to 1,200 years (sacred lotus) and 2,000 years (date palm). The percentage of viable seed decreases with age. Dormancy serves to enable the seed to survive poor growing conditions; a certain amount of embryonic development may also take place. Dormancy can be prolonged by extremely tough seed coats that exclude the water necessary for germination. Internally, growth is regulated by hormones called auxins. When the temperature is suitable and there is an adequate supply of moisture, oxygen, and light—although some seeds require darkness and others are unaffected by either—the seed absorbs water and swells, rupturing the seed coat. The growing tip (radicle) of the rudimentary root (hypocotyl) emerges first and then the growing tip (plumule) of the rudimentary shoot (epicotyl). Food stored in the endosperm or in the cotyledons provides energy for the early stages of this process, until the seedling is able to manufacture its own food via photosynthesisphotosynthesis
, process in which green plants, algae, and cyanobacteria utilize the energy of sunlight to manufacture carbohydrates from carbon dioxide and water in the presence of chlorophyll. Some of the plants that lack chlorophyll, e.g.
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the ability of a seed to yield normal sprouts after a set period of time in defined sprouting conditions. In the USSR seed germination is defined by state seed inspection in controlled seed analysis following a method prescribed by the All-Union State Standard (GOST 12038-66). The number of normally sprouted seeds is expressed as a percentage of the total number of seeds taken for analysis. In defining the usefulness of seeds for planting, germination is one of the most important qualities. This is of great productive importance. Seeds with high germination rapidly and conceitedly yield shoots, guaranteeing large harvests under proper conditions. High seed standards are required for norms of germination, so that first-class seeds of the basic grain crops except for hard wheat must have a germination not lower than 95 percent, and hard wheat must have one not lower than 90 percent. Seeds that do not meet the standard may not be used for planting. Germination depends to a great extent on the techniques of cultivation, method of harvesting, and storing conditions.
M. K. FIRSOVA