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Seedling
A seedling is a young sporophyte developing out of a plant embryo from a seed. Seedling development starts with germination of the seed. A typical young seedling consists of three main parts: the radicle (embryonic root), the hypocotyl (embryonic Shoot (botany), shoot), and the cotyledons (seed leaves). The two classes of flowering plants (angiosperms) are distinguished by their numbers of seed leaves: monocotyledons (monocots) have one blade-shaped cotyledon, whereas dicotyledons (dicots) possess two round cotyledons. Gymnosperms are more varied. For example, pine seedlings have up to eight cotyledons. The seedlings of some flowering plants have no cotyledons at all. These are said to be acotyledons. The plumule is the part of a seed embryo that develops into the shoot bearing the first true leaves of a plant. In most seeds, for example the sunflower, the plumule is a small conical structure without any leaf structure. Growth of the plumule does not occur until the cotyledon ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Seed
In botany, a seed is a plant structure containing an embryo and stored nutrients in a protective coat called a ''testa''. More generally, the term "seed" means anything that can be Sowing, sown, which may include seed and husk or tuber. Seeds are the product of the ripened ovule, after the embryo sac is fertilization, fertilized by Pollen, sperm from pollen, forming a zygote. The embryo within a seed develops from the zygote and grows within the mother plant to a certain size before growth is halted. The formation of the seed is the defining part of the process of reproduction in seed plants (spermatophytes). Other plants such as ferns, mosses and marchantiophyta, liverworts, do not have seeds and use water-dependent means to propagate themselves. Seed plants now dominate biological Ecological niche, niches on land, from forests to grasslands both in hot and cold climates. In the flowering plants, the ovary ripens into a fruit which contains the seed and serves to disseminate ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germination
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. Seed plants Germination is usually the growth of a plant contained within a seed resulting in the formation of the seedling. It is also the process of reactivation of metabolic machinery of the seed resulting in the emergence of radicle and plumule. The seed of a vascular plant is a small package produced in a fruit or cone after the union of male and female reproductive cells. All fully developed seeds contain an embryo and, in most plant species some store of food reserves, wrapped in a seed coat. Dormant seeds are viable seeds that do not germinate because they require specific internal or environmental stimuli to resume growth. Und ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Photomorphogenesis
In developmental biology, photomorphogenesis is light-mediated development, where plant growth patterns respond to the light spectrum. This is a completely separate process from photosynthesis where light is used as a source of energy. Phytochromes, cryptochromes, and phototropins are photochromic sensory receptors that restrict the photomorphogenic effect of light to the UV-A, UV-B, blue, and red portions of the electromagnetic spectrum. The photomorphogenesis of plants is often studied by using tightly frequency-controlled light sources to grow the plants. There are at least three stages of plant development where photomorphogenesis occurs: seed germination, seedling development, and the switch from the vegetative to the flowering stage ( photoperiodism). Most research on photomorphogenesis is derived from plants studies involving several kingdoms: Fungi, Monera, Protista, and Plantae. History Theophrastus of Eresus (371 to 287 BC) may have been the first to wr ite abo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cotyledon
A cotyledon ( ; ; "a cavity, small cup, any cup-shaped hollow", gen. (), ) is a "seed leaf" – a significant part of the embryo within the seed of a plant – and is formally defined as "the embryonic leaf in seed-bearing plants, one or more of which are the first to appear from a germinating seed." Botanists use the number of cotyledons present as one characteristic to classify the flowering plants (angiosperms): species with one cotyledon are called monocotyledonous ("monocots"); plants with two embryonic leaves are termed dicotyledonous ("dicots"). Many orchids with minute seeds have no identifiable cotyledon, and are regarded as acotyledons. The Dodders (''Cuscuta'' spp) also lack cotyledons, as does the African tree '' Mammea africana'' ( Calophyllaceae). In the case of dicot seedlings whose cotyledons are photosynthetic, the cotyledons are functionally similar to leaves. However, true leaves and cotyledons are developmentally distinct. Cotyledons form during embryo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Radicle
In botany, the radicle is the first part of a seedling (a growing plant embryo) to emerge from the seed during the process of germination. The radicle is the embryonic root of the plant, and grows downward in the soil (the shoot emerges from the plumule). Above the radicle is the embryonic stem or hypocotyl, supporting the cotyledon(s). It is the embryonic root inside the seed. It is the first thing to emerge from a seed and down into the ground to allow the seed to suck up water and send out its leaves so that it can start photosynthesizing. The radicle emerges from a seed through the micropyle. Radicles in seedlings are classified into two main types. Those pointing away from the seed coat scar or hilum are classified as ''antitropous'', and those pointing towards the hilum are ''syntropous''. If the radicle begins to decay, the seedling undergoes pre-emergence damping off. This disease appears on the radicle as darkened spots. Eventually, it causes death of the se ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypogeal Germination
Hypogeal germination (from Ancient Greek [] 'below ground', from [] 'below' and [] 'earth, ground') is a botanical term indicating that the germination of a plant takes place below the ground. An example of a plant with hypogeal germination is the pea (''Pisum sativum''). The opposite of hypogeal is epigeal (above-ground germination). __TOC__ Germination Hypogeal germination implies that the cotyledons stay below the ground. The epicotyl (part of the stem above the cotyledon) grows, while the hypocotyl (part of the stem below the cotyledon) remains the same in length. In this way, the epicotyl pushes the plumule above the ground. Normally, the cotyledon is fleshy, and contains many nutrients that are used for germination. Because the cotyledon stays below the ground, it is much less vulnerable to, for example, night-frost or grazing. The evolutionary strategy is that the plant produces a relatively low number of seeds, but each seed has a bigger chance of surviving. Pla ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryo
An embryo ( ) is the initial stage of development for a multicellular organism. In organisms that reproduce sexually, embryonic development is the part of the life cycle that begins just after fertilization of the female egg cell by the male sperm cell. The resulting fusion of these two cells produces a single-celled zygote that undergoes many cell divisions that produce cells known as blastomeres. The blastomeres (4-cell stage) are arranged as a solid ball that when reaching a certain size, called a morula, (16-cell stage) takes in fluid to create a cavity called a blastocoel. The structure is then termed a blastula, or a blastocyst in mammals. The mammalian blastocyst hatches before implantating into the endometrial lining of the womb. Once implanted the embryo will continue its development through the next stages of gastrulation, neurulation, and organogenesis. Gastrulation is the formation of the three germ layers that will form all of the different parts of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hypocotyl
The hypocotyl (short for "hypocotyledonous stem", meaning "below seed leaf") is the stem of a germinating seedling, found below the cotyledons (seed leaves) and above the radicle (root). Eudicots As the plant embryo grows at germination, it sends out a shoot called a radicle that becomes the primary root, and then penetrates down into the soil. After emergence of the radicle, the hypocotyl emerges and lifts the growing tip (usually including the seed coat) above the ground, bearing the embryonic leaves (called cotyledons), and the plumule that gives rise to the first true leaves. The hypocotyl is the primary organ of extension of the young plant and develops into the stem. Monocots The early development of a monocot seedling like cereals and other grasses is somewhat different. A structure called the coleoptile, essentially a part of the ''cotyledon'', protects the young stem and plumule as growth pushes them up through the soil. A mesocotyl—that part of the young plant that ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Epigeal Germination
Epigeal germination (Ancient Greek [] 'above ground', from [] 'on' and [] 'earth, ground') is a Glossary of botanical terms, botanical term indicating that the germination of a plant takes place above the ground. An example of a plant with epigeal germination is the common bean ('' Phaseolus vulgaris''). The opposite of epigeal is hypogeal (underground germination). , Epi: Above + Geo: Earth , + Germination __TOC__ Epigeal germination Epigeal germination implies that the cotyledons are pushed above ground. The hypocotyl elongates while the epicotyl remains the same in length. In this way, the hypocotyl pushes the cotyledon upward. Normally, the cotyledon itself contains very few nutrients in plants that show this kind of germination. Instead, the first leaflets are already folded up inside it, and photosynthesis starts to take place in it rather quickly.Parolin, P., Ferreira, L.V., Junk, W.J. (2003) ''Tropical Ecology'' 44(2): 157-169 Because the cotyledon is posit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phytochrome
Phytochromes are a class of photoreceptor proteins found in plants, bacteria and fungi. They respond to light in the red and far-red regions of the visible spectrum and can be classed as either Type I, which are activated by far-red light, or Type II that are activated by red light. Recent advances have suggested that phytochromes also act as temperature sensors, as warmer temperatures enhance their de-activation. All of these factors contribute to the plant's ability to germinate. Phytochromes control many aspects of plant development. They regulate the germination of seeds (photoblasty), the synthesis of chlorophyll, the elongation of seedlings, the size, shape and number and movement of leaves and the timing of flowering in adult plants. Phytochromes are widely expressed across many tissues and developmental stages. Other plant photoreceptors include cryptochromes and phototropins, which respond to blue and ultraviolet-A light and UVR8, which is sensitive to ultraviol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Etiolation
Etiolation is a process in flowering plants grown in partial or complete absence of light. It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow color (chlorosis). The development of seedlings in the dark is known as "skotomorphogenesis" and leads to etiolated seedlings. Effects Etiolation increases the likelihood that a plant will reach a light source, often from under the soil, leaf litter, or shade from competing plants. The growing tips are strongly attracted to light and will elongate towards it. The pale color results from a lack of chlorophyll. Some of the changes that occur include # elongation of stems and leaves; # weakening of cell walls in stems and leaves; # longer internodes, hence fewer leaves per unit length of stem; # chlorosis, a pale yellowish-white coloration. De-etiolation is the transition of seedlings from below-ground growth to above-ground growth form. Causes Etiolation is controlled by the plant hormone ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
