Buds and budding

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Buds and budding

Plant buds

Animal buds

Resources

Bud refers to three different types of undeveloped forms described in this article.

Plant buds

Plant buds, such as the buds of flowers, trees, and scrubs, are small, rounded, incompletely developed, dormant parts of a plant consisting of cells capable of rapid cell division when conditions are right for growth. They first appear in the spring when sap starts to flow, causing the buds to swell, which makes them more noticeable. These buds are first formed by the plant in late summer and early fall but remain small over the winter. When spring arrives, the structures for new shoot and floral growth are already formed and are tightly packaged and ready for quick growth when days lengthen and temperatures rise. The delicate, immature structures of these plant buds are covered with tough protective scales formed from modified leaves that enable the tender structures to get through winter in a dormant, resting state.

Plant buds can be classified in two ways, either according to their location on the plant, or according to the type of tiny immature structures that are contained within the bud. Buds on the tip of stems are called terminal buds, those at the sides of stems are called lateral buds, while those formed in the angle the leaf makes with the plant stem are known as axillary buds. When classified according to their internal structures, those that contain only the beginning of a flower are called flower buds. Those that contain only immature leaves are called leaf buds, while those buds containing both flowers and leaves in the earliest stages of development are termed mixed buds.

Flower buds on herbaceous plants and on woody plants are made up of undeveloped and tightly packed

groups of cells that are the precursors of the various floral partspetals, stamens, and pistilswith a whorl of sepals or outer leaf bracts covering and protecting the inner parts of the flower bud. Some small buds can produce a surprising amount of growth when attached to, and growing out from, a piece of the parent plant that is put into suitable soil. People familiar with growing potatoes by planting small sections of potato that contain eyes (sunken buds) know that the sprouts that grow from these buds will develop into whole new potato plants. Because of this remarkable ability for vegetative reproduction, these fertile pieces of potato are referred to as seed potatoes. The little sunken bud (the potato eye) draws its nourishment to sprout from the stored starchy food contained in the piece of parent potato tuber.

The buds that woody plants such as shrubs, woody vines, and trees produce contain miniature shoots with a short stem and small, undeveloped, tightly packed leaves or immature floral structures covered with tough protective, overlapping scales. A terminal bud on a woody twig overwinters and grows out during the next spring and summer into a whole new shoot that extends the length of the twig and may also produce flowers. Apple and cherry blossoms are

KEY TERMS

Dormant Inactive, but still alive. A resting non-active state.

Herbaceous A plant with the characteristics of an herb, it has little or no woody stems.

Vegetative propagation A type of asexual reproduction in plants involving production of a new plant from the vegetative structuresstem, leaf, or rootof the parent plant.

well known examples of this type of bud growth. Growth from a lateral bud will produce either a branch, or just a leaf on the side of the twig depending upon the nature of the precursor cells that were packaged in the bud during the previous fall.

Animal buds

Buds and budding are also found in the asexual reproduction (involving only one parent) of some animals, such as the freshwater hydra and species of marine colonial jellyfish, where a single parent gives rise to one or more new individuals. When a single hydra reaches maturity and is well fed, outpocketings of the animals body wall begin to form a rounded growth projecting from the tubelike section or stalk of the adults body. This growth, called a bud, develops in time into a miniature hydra whose body layers and inner body cavity, the digestive cavity, are continuous with that of the parent individual. Food captured and gathered in by the adult parent also supports the growth of the bud. Early in this budding process tiny tentacles appear on the free end of the hydra bud. It is not unusual to find two or more buds on an adult hydra in different stages of growth and development. An adult hydra may have its body and tentacles fully extended while its bud may have its whole form contracted into a rounded mass. Conversely the bud may be stretched out, while the adult is contracted. The bud will, however, sometimes contract soon after the adult contracts as the nerve net in the mesoglea (middle jelly layer) of the two individuals is continuous. When a newly budded hydra offspring is fully formed and sufficiently developed to take up an independent existence, the base of the new hydra seals off and thus allows the new individual to break off from the parent hydra.

Buds and budding also refers to the extensions of microscopic yeast cells and some types of bacterial cells produced during asexual reproduction, forming the beginning of daughter cells. The taste buds of the mammalian tongue, are so called because of their small size and bud-like shapes, but bear no relationship to the buds of plants and animals discussed above.

Resources

BOOKS

Campbell, N., J. Reece, and L. Mitchell. Biology. 5th ed. Menlo Park: Benjamin Cummings, Inc. 2000.

Raven, Peter, R.F. Evert, and Susan Eichhorn. Biology of Plants. 6th ed. New York: Worth Publishers Inc., 1998.

Julia M. Van Denack

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