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New plant grows out from a seed
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- Germination occurs when a new plant grows out from a seed. All seeds require three conditions for successful germination: Water allows the seed to swell up and all the chemical reactions involved in the growth of the embryo to take place.
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Germination. occurs when a new plant grows out from a seed. All seeds require three conditions for successful germination: Water allows the seed to swell up and all the chemical reactions...
- How do plants grow from a seed? - KS2 - The Regenerators ...
germination. . The root grows down to take up nutrients from...
- How do plants grow from a seed? - KS2 - The Regenerators ...
- Overview
- Seed dormancy
- Seedling emergence
germination, the sprouting of a seed, spore, or other reproductive body, usually after a period of dormancy. The absorption of water, the passage of time, chilling, warming, oxygen availability, and light exposure may all operate in initiating the process.
In the process of seed germination, water is absorbed by the embryo, which results in the rehydration and expansion of the cells. Shortly after the beginning of water uptake, or imbibition, the rate of respiration increases, and various metabolic processes, suspended or much reduced during dormancy, resume. These events are associated with structural changes in the organelles (membranous bodies concerned with metabolism), in the cells of the embryo.
Dormancy is brief for some seeds—for example, those of certain short-lived annual plants. After dispersal and under appropriate environmental conditions, such as suitable temperature and access to water and oxygen, the seed germinates, and the embryo resumes growth.
The seeds of many species do not germinate immediately after exposure to conditions generally favourable for plant growth but require a “breaking” of dormancy, which may be associated with change in the seed coats or with the state of the embryo itself. Commonly, the embryo has no innate dormancy and will develop after the seed coat is removed or sufficiently damaged to allow water to enter. Germination in such cases depends upon rotting or abrasion of the seed coat in the gut of an animal or in the soil. Inhibitors of germination must be either leached away by water or the tissues containing them destroyed before germination can occur. Mechanical restriction of the growth of the embryo is common only in species that have thick, tough seed coats. Germination then depends upon weakening of the coat by abrasion or decomposition.
In many seeds the embryo cannot germinate even under suitable conditions until a certain period of time has lapsed. The time may be required for continued embryonic development in the seed or for some necessary finishing process—known as afterripening—the nature of which remains obscure.
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The seeds of many plants that endure cold winters will not germinate unless they experience a period of low temperature, usually somewhat above freezing. Otherwise, germination fails or is much delayed, with the early growth of the seedling often abnormal. (This response of seeds to chilling has a parallel in the temperature control of dormancy in buds.) In some species, germination is promoted by exposure to light of appropriate wavelengths. In others, light inhibits germination. For the seeds of certain plants, germination is promoted by red light and inhibited by light of longer wavelength, in the “far red” range of the spectrum. The precise significance of this response is as yet unknown, but it may be a means of adjusting germination time to the season of the year or of detecting the depth of the seed in the soil. Light sensitivity and temperature requirements often interact, the light requirement being entirely lost at certain temperatures.
Active growth in the embryo, other than swelling resulting from imbibition, usually begins with the emergence of the primary root, known as the radicle, from the seed, although in some species (e.g., the coconut) the shoot, or plumule, emerges first. Early growth is dependent mainly upon cell expansion, but within a short time cell division begins in the radicle and young shoot, and thereafter growth and further organ formation (organogenesis) are based upon the usual combination of increase in cell number and enlargement of individual cells.
Until it becomes nutritionally self-supporting, the seedling depends upon reserves provided by the parent sporophyte. In angiosperms these reserves are found in the endosperm, in residual tissues of the ovule, or in the body of the embryo, usually in the cotyledons. In gymnosperms food materials are contained mainly in the female gametophyte. Since reserve materials are partly in insoluble form—as starch grains, protein granules, lipid droplets, and the like—much of the early metabolism of the seedling is concerned with mobilizing these materials and delivering, or translocating, the products to active areas. Reserves outside the embryo are digested by enzymes secreted by the embryo and, in some instances, also by special cells of the endosperm.
In some seeds (e.g., castor beans) absorption of nutrients from reserves is through the cotyledons, which later expand in the light to become the first organs active in photosynthesis. When the reserves are stored in the cotyledons themselves, these organs may shrink after germination and die or develop chlorophyll and become photosynthetic.
Environmental factors play an important part not only in determining the orientation of the seedling during its establishment as a rooted plant but also in controlling some aspects of its development. The response of the seedling to gravity is important. The radicle, which normally grows downward into the soil, is said to be positively geotropic. The young shoot, or plumule, is said to be negatively geotropic because it moves away from the soil; it rises by the extension of either the hypocotyl, the region between the radicle and the cotyledons, or the epicotyl, the segment above the level of the cotyledons. If the hypocotyl is extended, the cotyledons are carried out of the soil. If the epicotyl elongates, the cotyledons remain in the soil.
- John Heslop-Harrison
Feb 11, 2018 · Germination refers to the process by which an organism grows from a seed or a spore. The most common forms of germination include a seed sprouting to form a seedling and the formation of a sporeling from a spore. Thus, germination occurs primarily in plant and fungal species.
Feb 2, 2023 · Have you ever noticed a new plant to grow from the seed you have thrown away after eating? The process through which a new plant develops from its seed is called seed germination. Seed Germination Diagram. How do Seeds Germinate: The Process with Steps.
germination. . The root grows down to take up nutrients from the soil and the shoot grows up towards the sunlight to become a stem. The seed becomes a seedling. As this happens the plant is...
Germination is the process by which an organism grows from a seed or spore. The term is applied to the sprouting of a seedling from a seed of an angiosperm or gymnosperm, the growth of a sporeling from a spore, such as the spores of fungi, ferns, bacteria, and the growth of the pollen tube from the pollen grain of a seed plant.
Mar 19, 2014 · What happens when a seed germinates? Learn about the magic of seed germination, the process of a seed swelling and rupturing (what we call sprouting), and how to identify all the different parts of a seed and seedling (so you can understand why a seed might not germinate).
