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In botany, a bud is an undeveloped or embryonicshoot and normally occurs in the axil of a leaf or at the tip of the stem. Once formed, a bud may remain for some time in a dormant condition, or it may form a shoot immediately.
The buds of many woody plants, especially in temperate or cold climates, are protected by a covering of modified leaves called scales which tightly enclose the more delicate parts of the bud. Many bud scales are covered by a gummy substance which serves as added protection. When the bud develops, the scales may enlarge somewhat but usually just drop off, leaving on the surface of the growing stem a series of horizontally-elongated scars. By means of these scars one can determine the age of any young branch, since each year's growth ends in the formation of a bud, the formation of which produces an additional group of bud scale scars. Continued growth of the branch causes these scars to be obliterated after a few years so that the total age of older branches cannot be determined by this means.
In many plants scales are not formed over the bud, which is then called a naked bud. The minute underdeveloped leaves in such buds are often excessively hairy. Such naked buds are found in shrubs like the Sumac and Viburnums and in herbaceous plants. In many of the latter, buds are even more reduced, often consisting of undifferentiated masses of cells in the axils of leaves. A terminal bud occurs on the end of a stem and lateral buds are found on the side. A head of cabbage (see Brassica) is an exceptionally large terminal bud, while Brussels sprouts are large lateral buds.
Since buds are formed in the axils of leaves, their distribution on the stem is the same as that of leaves. There are alternate, opposite, and whorled buds, as well as the terminal bud at the tip of the stem. In many plants buds appear in unexpected places: these are known as adventitious buds.
Often it is possible to find a bud in a remarkable series of gradations of bud scales. In the buckeye, for example, one may see a complete gradation from the small brown outer scale through larger scales which on unfolding become somewhat green to the inner scales of the bud, which are remarkably leaf-like. Such a series suggests that the scales of the bud are in truth leaves, modified to protect the more delicate parts of the plant during unfavorable periods.
Types of buds
Buds are often useful in the identification of plants, especially for woody plants in winter when leaves have fallen. Buds may be classified and described according to different criteria: location, status, morphology, and function.
Botanists commonly use the following terms:
- for location:
- terminal, when located at the tip of a stem (apical is equivalent but rather reserved for the one at the top of the plant);
- axillary, when located in the axil of a leaf (lateral is the equivalent but some adventitious buds may be lateral too);
- adventitious, when occurring elsewhere, for example on trunk or on roots (some adventitious buds may be former axillary ones reduced and hidden under the bark, other adventitious buds are completely new formed ones).
- for status:
- accessory, for secondary buds formed besides a principal bud (axillary or terminal);
- resting, for buds that form at the end of a growth season, which will lie dormant until onset of the next growth season;
- dormant or latent, for buds whose growth has been delayed for a rather long time. The term is usable as a synonym of resting, but is rather employed for buds waiting undeveloped for years, for example epicormic buds;
- pseudoterminal, for an axillary bud taking over the function of a terminal bud (characteristic of species whose growth is sympodial: terminal bud dies and is replaced by the closer axillary bud, for examples beech, persimmon, Platanushave sympodial growth).
- for morphology:
- scaly or covered, when scales (which are in fact transformed and reduced leaves) cover and protect the embryonic parts;
- naked, when not covered by scales;
- hairy, when also protected by hairs (it may apply either to scaly or to naked buds).
- for function:
- vegetative, if only containing vegetative pieces: embryonic shoot with leaves (a leaf bud is the same);
- reproductive, if containing embryonic flower(s) (a flower bud is the same);
- mixed, if containing both embryonic leaves and flowers.
The term bud (as in budding) is used by analogy within zoology as well, where it refers to an outgrowth from the body which develops into a new individual. It is a form of asexual reproduction limited to animals or plants of relatively simple structure. In this process a portion of the wall of the parent cell softens and pushes out. The protuberance thus formed enlarges rapidly while at this time the nucleus of the parent cell divides (see: mitosis, meiosis). One of the resulting nuclei passes into the bud, and then the bud is cut off from its parent cell and the process is repeated. Often the daughter cell will begin to bud before it becomes separated from the parent, so that whole colonies of adhering cells may be formed. Eventually cross walls cut off the bud from the original cell.
Budding is a form of asexual reproduction in which a new organism grows on another one. The new organism remains attached as it grows, separating from the parent organism only when it is mature. Since the reproduction is asexual, the newly created organism is a clone and is genetically identical to the parent organism.
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Answers:actually, there are 9 kinds of asexual reproduction: *Binary fission-Many single-celled organisms (unicellular), such as Achaea, bacteria, and protists, reproduce asexually through binary fission *Budding Some cells split via budding (for example baker's yeast), resulting in a 'mother' and 'daughter' cell. *Vegetative reproduction Vegetative reproduction is a type of asexual reproduction found in plants where new independent individuals are formed without the production of seeds or spores. *Spore formation Many multicellular organisms form spores during their biological life cycle in a process called sporogenesis. *Fragmentation Fragmentation is a form of asexual reproduction where a new organism grows from a fragment of the parent. Each fragment develops into a mature, fully grown individual. *Parthenogenesis Parthenogenesis is a form of agamogenesis in which an unfertilized egg develops into a new individual. Parthenogenesis occurs naturally in many plants, invertebrates (e.g. water fleas, aphids, stick insects, some ants, bees and parasitic wasps), and vertebrates (e.g. some reptiles, amphibians, fish, very rarely birds). Agamogenesis Main article: Agamogenesis Agamogenesis is any form of reproduction that does not involve a male gamete. Examples are parthenogenesis and apomixis. *Apomixis Apomixis in plants is the formation of a new sporophyte without fertilization. It is important in ferns and in flowering plants, but is very rare in other seed plants. In flowering plants, the term "apomixis" is now most often used for agamospermy, the formation of seeds without fertilization, but was once used to include vegetative reproduction. *Nuclear Embryony Nucellar embryony occurs in some citrus seeds. Male apomixis can occur in rare cases, such as the Saharan Cypress where the genetic material of the embryo are derived entirely from pollen. The term "apomixis" is also used for asexual reproduction in some animals, notably water-fleas, Daphnia.
Answers:Budding occurs in yeast (for example), a fungus which consists of a single cells. A bulge called bud forms on the yeast cell.Its nucleus divides and a daughter cell goes into bud. The bud gets bigger until it eventually seperates to form a daughter cell. If growth condtions are good small buds may form on the larger onesbefore they have broken off . In this way chains of yeast cells are formed.
Answers:It's asexual reproduction because the DNA stays identical from parent to offspring and it only requires one organism to occur. In sexual reproduction, DNA from two parents needs to be combined to produce offspring.
Answers:1. sexual rep.= involves gametes asexual= without gametes BINary fission: a form of asexual reproduction mitosis: a type of cell reproduction which occurs in a somatic cell wherein one parent cell produces two daughter cells with the same no of chromosomes.