Difference between revisions of "Bud"

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[[image:buds.jpeg|thumb|right|Flower buds have not yet bloomed into a full-size flower.]]
 
[[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.
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[[Image:Bud1web.jpg|thumb|right|150px||]]
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An incipient or nascent [[shoot]]; the rudimentary or beginning state of a [[stem]]; particularly, in common speech, a thickened and condensed resting-stage of a shoot, or a flower or leaf before expanding; in [[propagating]], a single [[bud]] used on a [[cutting]] or [[cion]].
  
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.
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==Standard Cyclopedia of Horticulture==
[[Image:Bud1web.jpg|thumb|left|150px||]]
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Buds{{SCH}}. A bud is an incipient shoot or short growth- axis concealed by the closely investing leaves, or leaf- parts, that it bears. The foliage-shoots and flower-shoots of all seed plants arise from buds. The leaves converge over the true stem-apex or growing-point. The essential thing is that this growing-point continues the terminal growth and gives rise laterally, behind the point, to new leaves, in the axils of which buds may be formed ultimately. In the plumule of the seed the first bud activity is manifest, and thenceforth a bud marks every growing stem-apex.
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 [[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.
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Normally the leaves arise back of the stem-apex, first as small protuberances, which soon flatten laterally. They grow faster than the stem-apex, and by more rapid growth on the under surface they bend over, forming for the time a part of the bud or bud-cluster of leaves which effectively protects the delicate tip. In many herbaceous plants the shoot elongates throughout the growing period, so that each leaf or whorl of leaves in turn has a more or less equal work as a part of the bud. As the apex elongates and each leaf develops, greater growth on the inner (upper) surface effects its complete exfoliation. Using favorable material, one may completely dissect the bud, laying bare the growing- point, which may be readily examined with a hand- lens. Either of the little pondweeds commonly cultivated, Elodea or Hippuris, may be used for this purpose. The buds which are commonly most conspicuous and at the same time most highly specialized are the "resting" buds of temperate shrubs and trees. Such buds are often scaly buds, and they are characteristic of all climates in which there is an interruption to growth, either through cold or dryness. In this case the stem- apex and younger leaves are normally inclosed by persistent more or less indurated leaf-parts modified as bud-scales. Resinous secretions may accompany the scales and the younger leaves may be covered with hairs. The size, form and minute characters of such buds vary widely, but obviously they are, in general, wondrously efficient in the resistance exhibited towards rigorous climatic conditions. The important point is that the bud- structures quite effectually prevent drying out of the young shoot which is there tucked away.
  
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.
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Particularly interesting is the fact that the resting-bud of many trees includes in miniature the entire vegetative or flowering shoot of the next season. In such case the rapid elongation of the axis and unfoldingof leaves in the spring is soon followed by the formation of a new resting-bud wherein the shoot of another year is gradually differentiated. Every gradation occurs between this type and the fruit-buds on the left, typical active bud of annuals.  
  
==Types of buds==
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Interest in buds centers in their spring activity, properly in the awakening and growth resulting when the conditions have remained favorable sufficiently long. Leaves and axes enlarge and elongate rapidly, bursting asunder the dead scales and often carrying forward the expanding younger ones. The growth of the younger scales exhibits the true nature of these strictures, some of which are found to be leaf petioles, some petioles with minute blades; and various other modifications occur. Many resting- buds are awakened from their comparative inactivity by a few days of favorable weather. These are "early" flowers, and of this type are the lilac and the golden bell. Other buds require a longer period, such as the oak and the hickory. It is not strange, therefore, that some plants lend themselves readily to early forcing by etherization, the hot water treatment, and the like, while others are with great difficulty forced.
Since buds are short, embryonic stem tips, composed of resting leaves or flowers or both, they can be useful in the identification of plants and are often used for winter identification of woody plants. There are a few commonly used terms applied to buds by botanists:
 
  
'''Accessory''' - An extra bud produced on ether side of an axillary bud.<br />
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In the preceding, more specific mention has been made of buds which develop leafy shoots, that is of leaf-buds. It is clear, however, that the resting-bud, as well as an herbaceous bud, may develop a single flower, as in the peach; a cluster of flowers, as in the red maple; or a shoot with leaves and flowers, as in the apple and Norway maple. The occurrence of leaf- and flower-buds with respect to the age of the twig and the relation of pruning to bud disposition are questions of special horticultural interest, but cannot receive consideration in this brief account.  
'''Adventitious''' - Used to describe a bud that develops some place other than a stem node.  From roots or crown tissue or rhizomes.<br />
 
'''Axillary''' - When the buds are located in the axil of a leaf.<br />
 
'''Dormant''' - Non growing buds, were growth is delayed due to winter or dry conditions.<br />
 
'''Flower bud''' - A stem tip with embryonic flowers. Magnolia, Cherry.<br />
 
'''Lateral''' - Produced on the sides of the stems instead of at the ends.<br />
 
'''Leaf bud''' - A stem tip containing embryonic leaves.<br />
 
'''Mixed bud''' - Having both embryonic flowers and leaves.<br />
 
'''Naked''' - Not covered by a scaly covering.<br />
 
'''Pseudoterminal''' - Ustrrgfed for lateral buds that take over the function of the terminal buds, Common in persimmon.<br />
 
'''Reproductive''' - Having embryonic flowers.<br />
 
'''Scaly''' - Also called 'covered buds' which have bud scales that cover the embryonic flowers and/or leaves.<br />
 
'''Terminal''' - Buds at the ends of stems.<br />
 
'''Vegetative''' - Buds of embryonic leaves.<br /><br />
 
  
Bud scars are also often used for i
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Buds are normally produced terminally and in the axes of leaves, the latter arrangement therefore corresponding to leaves; but under exceptional circumstances they may arise from the growing tissue of any member. Buds from the roots of the sweet potato and dahlia are important in propagation; likewise are those produced by the leaves of certain species of Begonia. As a matter of fact, buds originating from internodes, roots and leaves—so-called regenerative-buds—are not uncommon; but the development in such situations occurs as a rule only when normal buds are not present.
dentification too, they are the scars left on stems after the buds have fallen away from the stems.
 
  
==Within zoology==
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Buds with the leaves and leaf-parts surrounding them are sometimes organs of food-accumulation. The typical bulb is little more than a fleshy bud, and there are all gradations between the typical bulb and the typical tuber-^the latter with many buds.. Small bulb-like buds occur in Liliurn bultriferum and a few other plants, and they are always important in propagation. It requires no stretch of the imagination to classify the edible shoots of brussels sprouts among unusual buds; and from this it is no great leap to the monstrous "bud" of the cabbage.
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.
 
  
 
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{{glossary}}
[[Category:Plant physiology]]
 

Latest revision as of 19:42, 18 February 2010

Flower buds have not yet bloomed into a full-size flower.
Bud1web.jpg

An incipient or nascent shoot; the rudimentary or beginning state of a stem; particularly, in common speech, a thickened and condensed resting-stage of a shoot, or a flower or leaf before expanding; in propagating, a single bud used on a cutting or cion.

Standard Cyclopedia of Horticulture

BudsCH. A bud is an incipient shoot or short growth- axis concealed by the closely investing leaves, or leaf- parts, that it bears. The foliage-shoots and flower-shoots of all seed plants arise from buds. The leaves converge over the true stem-apex or growing-point. The essential thing is that this growing-point continues the terminal growth and gives rise laterally, behind the point, to new leaves, in the axils of which buds may be formed ultimately. In the plumule of the seed the first bud activity is manifest, and thenceforth a bud marks every growing stem-apex.

Normally the leaves arise back of the stem-apex, first as small protuberances, which soon flatten laterally. They grow faster than the stem-apex, and by more rapid growth on the under surface they bend over, forming for the time a part of the bud or bud-cluster of leaves which effectively protects the delicate tip. In many herbaceous plants the shoot elongates throughout the growing period, so that each leaf or whorl of leaves in turn has a more or less equal work as a part of the bud. As the apex elongates and each leaf develops, greater growth on the inner (upper) surface effects its complete exfoliation. Using favorable material, one may completely dissect the bud, laying bare the growing- point, which may be readily examined with a hand- lens. Either of the little pondweeds commonly cultivated, Elodea or Hippuris, may be used for this purpose. The buds which are commonly most conspicuous and at the same time most highly specialized are the "resting" buds of temperate shrubs and trees. Such buds are often scaly buds, and they are characteristic of all climates in which there is an interruption to growth, either through cold or dryness. In this case the stem- apex and younger leaves are normally inclosed by persistent more or less indurated leaf-parts modified as bud-scales. Resinous secretions may accompany the scales and the younger leaves may be covered with hairs. The size, form and minute characters of such buds vary widely, but obviously they are, in general, wondrously efficient in the resistance exhibited towards rigorous climatic conditions. The important point is that the bud- structures quite effectually prevent drying out of the young shoot which is there tucked away.

Particularly interesting is the fact that the resting-bud of many trees includes in miniature the entire vegetative or flowering shoot of the next season. In such case the rapid elongation of the axis and unfoldingof leaves in the spring is soon followed by the formation of a new resting-bud wherein the shoot of another year is gradually differentiated. Every gradation occurs between this type and the fruit-buds on the left, typical active bud of annuals.

Interest in buds centers in their spring activity, properly in the awakening and growth resulting when the conditions have remained favorable sufficiently long. Leaves and axes enlarge and elongate rapidly, bursting asunder the dead scales and often carrying forward the expanding younger ones. The growth of the younger scales exhibits the true nature of these strictures, some of which are found to be leaf petioles, some petioles with minute blades; and various other modifications occur. Many resting- buds are awakened from their comparative inactivity by a few days of favorable weather. These are "early" flowers, and of this type are the lilac and the golden bell. Other buds require a longer period, such as the oak and the hickory. It is not strange, therefore, that some plants lend themselves readily to early forcing by etherization, the hot water treatment, and the like, while others are with great difficulty forced.

In the preceding, more specific mention has been made of buds which develop leafy shoots, that is of leaf-buds. It is clear, however, that the resting-bud, as well as an herbaceous bud, may develop a single flower, as in the peach; a cluster of flowers, as in the red maple; or a shoot with leaves and flowers, as in the apple and Norway maple. The occurrence of leaf- and flower-buds with respect to the age of the twig and the relation of pruning to bud disposition are questions of special horticultural interest, but cannot receive consideration in this brief account.

Buds are normally produced terminally and in the axes of leaves, the latter arrangement therefore corresponding to leaves; but under exceptional circumstances they may arise from the growing tissue of any member. Buds from the roots of the sweet potato and dahlia are important in propagation; likewise are those produced by the leaves of certain species of Begonia. As a matter of fact, buds originating from internodes, roots and leaves—so-called regenerative-buds—are not uncommon; but the development in such situations occurs as a rule only when normal buds are not present.

Buds with the leaves and leaf-parts surrounding them are sometimes organs of food-accumulation. The typical bulb is little more than a fleshy bud, and there are all gradations between the typical bulb and the typical tuber-^the latter with many buds.. Small bulb-like buds occur in Liliurn bultriferum and a few other plants, and they are always important in propagation. It requires no stretch of the imagination to classify the edible shoots of brussels sprouts among unusual buds; and from this it is no great leap to the monstrous "bud" of the cabbage.


This article contains a definition from the Glossary of Gardening Terms.