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
twigs by
the female Cynips Gallae-tinctoriae, who lays its eggs inside. This species of
oak seldom attains the height of 6 feet, the stem being crooked, 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
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