Gallengruppe
allgemein Anhängsel
[D.S. Kimball]
Galls are excrescences produced in plants by the presence of the larvae
of different insects. The forms that they assume are many, and the changes
produced in the tissues various.
They occur in all parts of the plant.
The oak galls used in commerce and medicine are excrescences on Quercus
infectoria, a small oak, indigenous to Asia Minor and
with the habit of a shrub rather than a tree.
The Common Oaks of this country are much affected by galls. They occur
sometimes on the leaves, where they form the so called 'Oak-apples,' sometimes
on the shoots, where they do great mischief by checking and distorting the
growth of the tree.
The young larva that hatches from the eggs feeds upon the tissues of the
plant and secretes in its mouth a peculiar fluid, which stimulates the cells of
the tissues to a rapid division and abnormal development, resulting in the
formation of a gall.
The larva thus becomes completely enclosed in a nearly spherical mass,
which projects from the twig, furnishing it with a supply of starch and other
nutritive material.
The growth of the gall continues only so long as the egg or larva lives
or reaches maturity and passes into a chrysalis, from which the fully-developed
gall-wasp emerges and escapes into the air through a hole bored with its
mandibles in the side of the gall.
The best
Galls are also largely imported from
Aleppo Galls of good quality are hard and heavy, without perforations,
dark bluish-green or olive green, nearly spherical in shape, 12 to 18 mm. in
diameter (about 2/5 to 4/5 inch), (blue or green galls in commerce).
The
the fruit so pleasant to the eye, so bitter to the taste.
Collected after the insects have escaped, galls are of a pale,
yellowish-brown hue, spongy and lighter in weight, perforated near the centre
with a small hole. Known as white galls. On breaking a gall, it appears yellowish
or brownish-white within, with a small cavity containing the remains of a larva
of the Gall-wasp.
Galls have no marked odour, but an intensely astringent taste, and
slightly sweet after-taste.
Source, History, and Formation: Though existing in a number of
astringent plants, the greater portion of commercial gallic acid is derived
from nutgalls. Scheele (1785),
who first obtained it pure, established its non-identity with tannic
acid. The manner of formation of gallic acid from nutgalls has been a subject
of much discussion and experimentation. Before investigations were begun it was
believed to exist ready-formed in galls, but in 1833 Pelouze showed that the
larger portion of it was derived from
the tannin of the galls, and advanced the theory that this conversion
was accomplished by oxidization by the atmospheric oxygen, by which carbon
dioxide was driven off. The elder Robiquet (1837) showed that its conversion
could be accomplished without the aid of oxygen and without evolving carbon
dioxide, but that it resulted from
a ferment called pectase. Wetherill (1847), and subsequently, Mulder
(1848), attempted to show that tannic acid differed from gallic acid only in
the possession of a larger amount of water of crystallization. Liebig believed
the change to be due to the liberation of a carbohydrate. In 1854 Strecker came
to the conclusion that tannin was a glucosid, for by boiling it with diluted
mineral acid he obtained a large amount of gallic acid and considerable
glucose. This view was generally accepted for a long time, though opposed by
the younger Robiquet (1854) and Hlasiwetz (1867), who advanced different
theories regarding the supposed glucosid. Present theory: advanced by Schiff
(1871) and supported by others, that pure tannic acid be viewed as digallic
acid (this being the first anhydrid of gallic acid), and that natural tannin is
the glucosid of pure tannic,
or digallic acid, for by the action of hot diluted mineral acids or a
nitrogenous ferment upon it, digallic acid and glucose are evolved.
The biosynthetic pathway of gallic acid in leaves of Rhus typhina is
studied by oxygen isotope ratio mass spectrometry at natural oxygen isotope
abundance. The observed delta18O-values of gallic acid indicate an
18O-enrichment of the phenolic oxygen atoms of more than 30 per thousand above
that of the leaf water. This enrichment implies biogenetical equivalence with
oxygen atoms of carbohydrates but not with oxygen atoms introduced by
monooxygenase activation of molecular oxygen. It can be concluded that all
phenolic oxygen atoms of gallic acid are retained from the carbohydrate-derived
precursor 5-dehydroshikimate. This supports that gallic acid is synthesized
entirely
or predominantly by dehydrogenation of 5-dehydroshikimate.
COMMON OAK GALLS
[Lee Townsend, Extension Entomologist, and Eileen Eliason]
Galls are irregular plant growths which are stimulated by the reaction
between plant hormones and powerful growth regulating chemicals produced by
some insects or mites. Galls may occur on leaves, bark, flowers, buds, acorns,
or roots. Leaf and twig galls are most noticeable. The inhabitant gains its
nutrients from the inner gall tissue. Galls also provide some protection from
natural enemies and insecticide sprays. Important details of the life cycles of
many gall-makers are not known so specific recommendations to time control
measures most effectively are not available.
Gall makers must attack at a particular time in the year to be
successful. Otherwise, they may not be able to stimulate the plant to produce
the tissue which forms the gall.
Generally, initiation of leaf galls
occurs around "bud break" or as new leaves begin to unfold in the
spring.
Twig and Stem Galls
Such as the gouty oak gall and horned oak gall, are solid, woody masses
that can girdle branches or make them droop from the sheer weight of the heavy
growths.
The galls can grow to more than 2 inches in diameter. Horned oak galls
can be found on pin, scrub, black, blackjack, and water oaks while gouty oak
galls occur on scarlet,
red, pin or black oak.
These galls have a long and complex development that takes two or more
years to develop. The first stage is a blister-like leaf gall that occurs along
larger leaf veins.
The second stage is a knotty twig gall that is started in mid-summer and
becomes fully mature in 1 - 2 yrs. Adults emerge in the spring.
Gouty oak twig galls are smooth; hormed oak galls have horn-like
projections. One female wasp can emerge from each horn.
Generally, insecticidal control is not satisfactory because the wasps
are physically protected within the galls. Correctly timing applications to
provide effective preventive control is difficult. Where practical, pruning of
infested twigs may help to reduce the problem on lightly-infested trees.
However, pruning is impractical if large trees are heavily infested. A
commercial arborist may be able to provide assistance with valuable plantings.
Vorwort/Suchen Zeichen/Abkürzungen Impressum