Bud 43604 224392267 2008-07-08T17:28:48Z Nburden 3083182 Reverted 1 edit by [[Special:Contributions/99.135.170.229|99.135.170.229]] identified as [[WP:VAND|vandalism]] to last revision by [[User:Fireaxe888|Fireaxe888]]. ([[WP:TW|TW]]) {{unreferenced|date=June 2008}} {{otheruses}} [[image:buds.jpeg|thumb|right|Flower buds have not yet bloomed into a full-size flower.]] In [[botany]], a '''bud''' is an undeveloped or [[Plant embryogenesis|embryonic]] [[shoot]] and normally occurs in the [[axil]] of a [[leaf]] or at the tip of the [[Plant stem|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 [[wood]]y [[plant]]s, 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 [[scar]]s. 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. [[Image:Bud1web.jpg|thumb|left|150px||]] In many plants scales are not formed over the bud, which is then called a naked bud.<ref>Walters, Dirk R., and David J. Keil. 1996. ''Vascular plant taxonomy''. Dubuque, Iowa: Kendall/Hunt Pub. Co. page 598.</ref> The minute underdeveloped leaves in such buds are often excessively hairy. Such naked buds are found in shrubs like the [[Sumac]] and [[Viburnum]]s 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 sprout]]s 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.<ref>Coulter, John G. 1913.'' Plant life and plant uses; an elementary textbook, a foundation for the study of agriculture, domestic science or college botany''. New York: American book company. page 188</ref> Often it is possible to find a bud in a remarkable series of gradations of bud scales. In the [[Aesculus|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== [[Image:Plant Buds clasification.svg|270px|right|Plant Buds classification]] Buds are often useful in the identification of plants, specially for woody plants in winter when leaves have fallen.<ref>http://ohioline.osu.edu/b700/b700_07.html</ref> Buds may be classified and described according to different criteria : location, status, morphology, 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 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), **'''dormant''', for buds whose growth has been delayed for a rather long time (the term is usable for buds resting during winter or dry season, but is rather employed for buds waiting undeveloped for years), **'''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]], ''[[Platanus]]'' have 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. ==Within zoology== 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 (biology)|cell]] softens and pushes out. The protuberance thus formed enlarges rapidly while at this time the [[cell nucleus|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. ==References== {{Reflist}} [[Category:Plant physiology]] [[ast:Xema (bioloxía)]] [[cs:Pupen]] [[da:Knop (plantedel)]] [[de:Knospe]] [[es:Yema]] [[eo:Burĝono]] [[fr:Bourgeon (botanique)]] [[he:ניצן]] [[it:Bulbo]] [[ka:კვირტი]] [[lt:Pumpuras]] [[nl:Knop (plant)]] [[ja:蕾]] [[pl:Pąk]] [[pt:Gomo (botânica)]] [[ro:Mugur]] [[ru:Почка (ботаника)]] [[tl:Buko (usbong)]] [[tr:Tomurcuk]] [[uk:Брунька]]