Gall, Sioux war chief
, c.1840–1894, war chief of the Sioux, b. South Dakota. He refused to accept the treaty of 1868 (by which he would have been confined to a reservation), joined Sitting Bull
and other dissident chiefs, and was the chief military lieutenant of Sitting Bull in the great defeat of George Armstrong Custer in the battle of Little Bighorn in 1876. He retreated to Canada but, after a quarrel with Sitting Bull about returning to their former lands, returned and surrendered at Poplar, Mont. He became a farmer on the reservation and with his friend James McLaughlin, the Indian agent, did much to improve relations between Native Americans and whites.
See T. B. Marquis, Sitting Bull and Gall (1934).
gall, in botany
gall, abnormal growth, or hypertrophy, of plant tissue produced by chemical or mechanical (e.g., the rubbing together of two branches) irritants or hormones. Chemical irritants are released by parasitic fungi, bacteria, nematode worms, gall insects, and mites. Crown gall, which attacks peach and other fruit trees, grapes, and roses, is caused by bacteria. Despite its name (the crown is the head of foliage), the tumorous growths usually occur on the stem below ground level. The gall insects (e.g., certain aphids, wasps, moths, beetles, and midges) deposit their eggs in the plant tissues, which begin to swell as the larvae hatch. Sometimes the larvae feed on the gall and pupate within it. The irritant is released by the female at the time of oviposition or by the developing larva itself. Each species of gall insect has its favorite host and forms galls of a characteristic shape; some are large and woody and others may be soft, knobby, or spiny. They may be formed on any part of a plant but generally occur in areas where cells are actively growing. In the United States, Galls are commonly seen on oak and willow trees and on rose bushes, goldenrod, and witch hazel. The Hessian fly, the wheat midge, and the mites and midges that attack fruit trees are the most damaging economically of the gall insects. Galls are rich in resins and tannic acid and have been used in the manufacture of permanent inks and astringent ointments, in dyeing, and in tanning. A high-quality ink has long been made from the Aleppo gall, found on oaks in the Middle East; it is one of a number of galls resembling nuts and called gallnuts or nutgalls.
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A neoplastic disease of primarily woody plants, although the disease can be reproduced in species representing more than 90 plant families. The disease results from infection of wounds by the free-living soil bacterium Agrobacterium tumefaciens which is commonly associated with the roots of plants.
The first step in the infection process is the site-specific attachment of the bacteria to the plant host. Up to half of the bacteria become attached to host cells after 2 h. At 1 or 2 weeks after infection, swellings and overgrowths take place in tissue surrounding the site of infection, and with time these tissues proliferate into large tumors (see illustration). If infection takes place around the main stem or trunk of woody hosts, continued tumor proliferation will cause girdling and may eventually kill the host. Crown gall is therefore economically important, particularly in nurseries where plant material for commercial use is propagated and disseminated.
Crown gall on peach
Unlike healthy normal cells, crown gall tumor cells do not require an exogenous source of phytohormones (auxins and cytokinin) for growth in culture because they readily synthesize more than sufficient quantities for their own growth. They also synthesize basic amino acids, each conjugated with an organic acid, called opines. The tumor cells also grow about four times faster and are more permeable to metabolities than normal cells.
These cellular alterations, such as the synthesis of opines and phytohormone regulation, result from bacterial genes introduced into host plant cells by A. tumefaciens during infection. Although it is not understood how these genes are introduced into the plant cell, the genes for the utilization of these opines and for regulating phytohormone production have been found to be situated on an extrachromosomal element called the pTi plasmid. This plasmid, harbored in all tumor-causing Agrobacterium species, also carries the necessary genetic information for conferring the tumor-inducing and host-recognition properties of the bacterium.
Crown gall is consequently a result of this unique bacteria-plant interaction, whereby A. tumefaciens genetically engineers its host to produce undifferentiated growth in the form of a large tumor, in which there is the synthesis of a unique food source in the form of an opine for specific use by the bacterial pathogen. See Bacterial genetics, Genetic engineering, Plant hormones, Plant pathology
McGraw-Hill Concise Encyclopedia of Bioscience. © 2002 by The McGraw-Hill Companies, Inc.
crown gall[′krau̇n ‚gȯl]
A bacterial disease of many plants induced by Bacterium tumefaciens and marked by abnormal enlargement of the stem near the root crown.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.