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Printed in India
Organisms and Environment
By
Anup Kumar Sarkar
EDUCREATION PUBLISHING
(Since 2011)
www.educreation.in
ISBN: 978-93-89808-99-5
1
Praface
Environment is the essential requirement for the survival of all types of
organisms including human. For the survival of all organisms a healthy
stretches of environmental factors is very needed. Contrary organisms impart
their apparently positive and negative impacts on environmental factors.
Sound knowledge about environment and organisms and their interactions
are essential as man have to live with nature and other organisms. In
present time Scientific activities plays a very pivotal role for environment
friendly sustainable development. In this volume we have tried to make a
little step forward to a thorough understanding of interactions between
Environmental factors and different organisms and their effect on mankind.
The book provides some basic and prime information on few dimensions of
nature, environment and organisms.The book is dedicated to the students,
researchers and academicians in the field. I hope this book will also helpful
to inform and improve decision-making for the management of sustainable
development.
Now I express my deepest gratitudes to the contributing authors for their
contributions. I also apologize to the personnels whose articles have not been
accommodated here. I conface that all the manuscript submitted for the
volume, were of excellent quality to be selected for publication in this book,
but some of them have been placed in this modest volume.
I am also greatful to my family and colleagues of Dukhulal Nibaran Chandra
College for extending their helping hands as and when required.
In total this book is an attempt to contribute in the field of Sciences. I hope
that this edited book will be very useful to the academicians, researchers
and students in this field.
Anup Kumar Sarkar
Assistant Professor
Department Of Botany
Dukhulal Nibaran Chandra College
Murshidabad,West Bengal,India
Organisms and Environment
180
Abstract:
Caring of ecosystem is the cultural, social and spiritual legacy that we have inherited from our
past and pass on to the future. World ecosystem is unique in its reverence for Mother Nature in
all her manifestations. Ancient traditions, rituals, practices have embedded this reverence in
religion and even in normal day-to-day living. The respect for nature and the belief that every
organism on earth has a special role in life’s cycle forms the care of our ecological ecosystem.
Plant galls are out- burst of repulsive reactions of the plant tissues to the stimulus incited by
certain guild of phytophagous insects. The ultimate effort of the gall inducing insects is to secure
nutrition and safe domain for a short span of time during their life-cycle. In certain instances,
these needs are fulfilled by the development of a simple outgrowth of the plant organ, a
structure termed ‘gall’, which provides the food and shelter to the gall-inducing insects and
mites. In many cases, the galls induced by the parasites attain phenomenal structural
complexity and architectural design which have allured the naturalists. Our knowledge of plant-
galls dates back to Seventeenth century, and Marcello Malpighi seems to have held the
foundation for the scientific perspectives of the plant galls. Different research centers have been
contemplating on the various aspects of cecidogenetic studies and striving to reach solutions for
resolving certain intrigue queries involved in the cecidogenetic mechanism. The distribution of
galls in India presents several interesting and significant facts. The floristic compositions of
Indian sub-continent is highly varied which in turn reflects the diversified climatic and edaphic
factors. The phytophagous insects, particularly the gall-inducing insects are highly circum-
scribed to specific ecoregions and to the specific host plants. The flora of temperate zones
harbours specific types of galls and their associated insects; the tropical plants are also specific
in bearing galls of specific insect species. Though the gall-population status and infestation rate
are low in the environment, the morphological spectrum and structural complexity of the galls
are splendid and alluring. High degree of specificity of host plants, host organs or tissues,
morphological exposition and internal organisation with reference to the gall inducing agents is
the striking phenomenon observed in the ecosystem. All about environment, it’s about gall. It is
truly a pathological structure it comes under environmental factors. It shows special accent
towards ecological relationship and also their impacts towards economic and medicinal field and
even parasitic, symbiotic system is recorded in galls towards environment. They play a key role
in ecological balance.
Key words:
Ecosystem, Environment, Insects, Mites, Plant Galls.
1. Introduction:
Plants are the basis of the food pyramid for all living things even other plants and insects. Since
Vedic times Indians have regarded lakes, mountains, seeds, plants and animals as sacred and
worthy of protection. People protected the groves to express their reverence for the sources of
their survival. Urbanization is a common and inevitable occurrence everywhere. While growth
and expansions are beneficial for many people and businesses, there is a potential for loss of
biodiversity areas that are of ecological important. India is very rich in terms of biological
diversity due to its unique biogeographic location, diversified climatic conditions and enormous
Plant Galls-A Biological Puzzle
M. Gopi
Department of Plant Biology and Plant Biotechnology,Guru Nanak College,
Guru Nanak Salai, Velachery, Chennai,Tamilnadu,India, Pin-600 042.
Corresponding Author’s E-mail id: gopi.m@gurunanakcollege.edu.in
ISBN: 978-93-89808-99-5
181
ecodiversity and geodiversity. The insects are by far the largest group among animals and plants
in the world. It has been referred to as Patanga, Shalabh, Bhramar, Pipilika, Makshika,
Shadpada, Laksha Keet etc., in ancient Sanskrit writings. It is commonly believed that 75–80 %
of the total animal species on this planet are insects. They are found in everywhere, except in
seas and oceans. The factors such as their minute size, high fecundity, capacity for flight and
dispersal, ability to feed on variety of materials, water retention capability, presence of chitinous
exoskeleton, etc., are important for their survival in different type of ecosystems with success.
Based on the data currently collected from the experts of different groups and compared with
those known from the world is quite evident that India possesses little more than 7 per cent of
the total animal species of the world. It is higher than that of the plant species. Out of total
86,874 animal species of this country Insects alone comprise 68.32 per cent (Alfred, J.R.B,
1998). Thus, both in quality (number of species) and quantity (number of individuals) they
outnumber all other biota. India provides wide range of ecological, climatic and vertical
distribution of the insect population. The current corrected figures are 619 families and 59,353
species of insects from India. The tropical evergreen forests of eastern Himalaya and hills of the
north eastern India harbor maximum number of species. There are still areas that have not been
adequately explored for its insect wealth. It will be interesting to note that insects have adapted
to the flowering plants (which evolved later than earliest insects) in a big way. A large number of
insects feed on plants, including economically important plants and crops. The latter are thus
termed as pests. It is for this reason that insects have been called man’s worst enemy. Besides
these habitats, insects are also found on fungi, algae, moss, lichen, rotten wood, leaf litter,
under logs, under stones, carrions, dung and other excreta, under bark, in books and papers,
wood piles, godowns, haystacks, granaries, on or below snow; on electric light; in running and
stagnant waters; in clothes and burrows in ground. Some insects make galls and mines in
different parts of the plants and live there. So far there has been no indepth and standard study
of the enumeration of endemic taxa of insects in India for many reasons. Besides, insects are
carriers of diseases in men and domestic animals. For the spread of number of serious diseases
like malaria, yellow fever, dengue etc., the insects are primarily to be blamed. However, the
beneficial side is no less valuable, as the insects are the pollinators of plants, thus they play an
important role in the nature. They serve as food for other insects, spiders fishes, birds, etc.,
forming a vital link in the food chain. Among the beneficial insects, there are foremost -the
honey bee, the silk moth and the lac insect. There are four kinds of silks produced in the
country from different silk moths. For biological control, some insect species which are either
predaceous or parasitic on other insect or mite pests have been utilized the world over. Some
other insect species have been found useful in the control of weeds like Lantana, Opuntia and
Parthenium. Conservation of habitat is equally important in case of insects as in the cases of
other animals. Since many insects are forest dwellers, afforestation can help in saving some of
the insect species from the danger of extinction. Protection of wetlands from pollution and other
human interference will be helpful in safeguarding aquatic insect populations. Galls are unique
growths induced by plants in response to the feeding or oviposition stimulus of insects resulting
in excessive growth and cell multiplication. In almost all instances of cecidogenous insects, galls
induced on juvenile plant organs, through rarely on mature stems or leaves. From the nature
and the morphology of the galls formed, it is evident that gall-insects are clearly species-specific.
While feeding and reproduction are basic functions evident in insect-plant interactions, there are
many other facets to the study of their interactions, the notable among them being pollination,
gall production as well as development of resistance in plants to insect attack.
2. Plant Galls:
Plant galls are external expression of mysterious interaction between two biological entities
namely the plant and insect. The gall inducer, which are phytophagous parasites are dependent
on the plant tissues not only to feed on, but also for an ideal niche to live in during a short
duration of their life-cycle. During the feeding or ovipositing efforts of the animal parasites on
the plant organs, a series of action-reaction system is established between the parasites and
their host plants. A compromise is reached at the end of the processes and a structure called
“Gall” is produced by the plant organs. The gall thus produced provides quality nutrition as
Organisms and Environment
182
well as safe domain to the gall-inducers and at the same time, the plants are able to localize
them in space and time, thus the gall-inciting agent is physically and physiologically isolated
and is driven to extreme specialization with respect to its various biological activities.
Insect-induced plant galls were known to humans for long, mostly for use as drugs and for
extracting ink-like material used in writing and painting. Until the early decades of the 19th
century, those who studied galls and their inhabitants referred to these plant abnormalities as
galls only. Friedrich Thomas first used the term ‘cecidium’ in 1873, deriving it from kekis
(Greek), which means ‘something abnormal with an oozing discharge’. Consequently, the study of
galls came to be known as Cecidology. One significant name in cecidology is Alessandro Trotter
(1874-1967). He founded Marcellia, a journal dedicated to cecidology, in 1902, which serviced
science untiles the 1980s (Raman, 2019).
Galls arise on all classes of plants, for example algae, mosses, ferns, gymnosperms, dicotyledons
and monocotyledons. They may arise on underground and aerial roots, shoot axis, petioles,
stipules, leaf blade and leaf veins, vegetative and flower buds, inflorescence axis, bracts, flowers
and fruits. South Indian forests present more varied flora than any other tract of equal area in
India, possibly in the World, a phenomenon due to the combined effects of its geographical
situation and its topography (Gamble, 1935). South Indian forests comprise of five main floristic
regions, namely, Sal region, Dekkan region, Semi-desert region, Wet region and Alpine region.
These floristic regions are characterized by distinct floras and faunas, which are highly
influenced by specific ecological factors.
The shola forests are mostly evergreen with shotbold and branchy trees. Trees very rarely exceed
6 m height. The crowns are usually very dense and rounded. Branches are often seen clothed
with mosses, ferns and other epiphytes. Woody climbers are also quite common and canopy
layers are difficult to distinguished. Western Ghats have almost a continuous physical extension
close to the West coast from Nilgiris to south Kanyakumari of Tamil Nadu, but the Eastern
Ghats are not only rather irregular in their extension and altitude but also are, further away
from east coast of Tamil Nadu and extend between Salem, Dharmapuri, Coimbatore. North and
South Arcot districts. The highest peaks of Western Ghats in Tamil Nadu are Dodabetta ( 2637
m) and Anaimudi (2695 m). Whereas the average height of the Eastern Ghats may be taken as
about 600 m only. Nature has endowed Eastern and Western Ghats of Tamil Nadu with
impressively diverse plant taxa.
Dispersal of plant galls whether passive mode or active mode, is greatly influenced by
geographical routes or barriers. Routes i.e. plants favour dispersal and provide access to new
areas. But the barriers i.e. insects limit dispersal of galls. So the plant galls biogeography is
restricted and limited to certain areas only. Dispersal, population size and reproductive
potentials are parts of ecological valence of the plants or animal. The ecological valence is a
measure of the reaction of the species to the environmental influences. For the galls the
ecological valence is narrow and they are stenotypes, occur under only well defined, limited set
of conditions, such a species is too specialized to occur elsewhere. Even if a plant gall
successfully overcome a barrier and has reached a region, it can actually established itself only
if the conditions are favourable. Unfavourable conditions of temperature, humidity, rainfall and
other climatic factors may wipe out the galls. The continued existence of galls is then possible in
an area is depend on thermal constant which directly influences development, growth of plant,
breeding cycles of insects etc. For example the galls in shoal forests cannot colonize area like
dry-scrub forests (Mani, 2000). In biogeography of plant galls the plants and the insects cannot
be isolated from each other. They together represent an inseparable complex or community with
interdependent, hierarchial levels of states and divisions of functions. Together with non-living
background thus complex makes an ecosystem, in which all members are bound together in an
intricate food-chain. So the distribution of gall insects is thus closely bound up with that of its
specific plants. Plants constitute an essential part of the natural habitats, with which all gall
insect life is inseparably bound up (Mani,1964).
Galls are extremely varied in size and appearance and in their location on the plant body. They
vary in consistency from relatively soft to hard and woody; many are brightly coloured. The gall
ISBN: 978-93-89808-99-5
183
surface may be smooth, knobby, velvety or spiny. A gall, consisting exclusively of erineal
outgrowths, is known as filz gall. The abnormal cell growth and multiplication, are confined
wholly to the epidermal cells, thus giving rise to emergent galls of undifferentiated, excessively
elongated hairy outgrowths called erineum. When the cecidogenetic centre lies in the
subepidermal layers of the cortex of shoot or root, it is known as rinden galls. When
cecidogenesis is on the shoot axis or petiole, the plant tissue grows around and above, so as to
enclose the cecidozoen that lies initially exposed on the surface of the plant. Such galls are
otherwise called covering growth galls.
The simplest leaf galls are fold galls, in which the unfolding of the leaf rudiment of the
developing bud is suppressed. In the leaf roll galls, the blade rolls upward. Many complex leaf
galls are sessile or stalked, more or less swollen pouch-like outpockteings, mostly on the upper
surface of the blade. These constitute the pouch galls. Arresting of the elongation of internode,
results in a rosette-gall.
The flower galls, range from simple crumpling of sepals and petals to complex fusion and
swelling of sepals, petals, stamens, pistil and even bracts into a composite fleshy or hard mass,
in which the individual floral parts cannot be recognized. Some galls are hollow and enclose one
or more, smaller or larger gall cavities, containing the cecidozoa. In atriate galls, there is an
accessory space or atrium in addition to the gall cavity proper. The gall cavity is lined by small,
closely packed mass of cells, rich in cell contents and they constitute the nutritive tissue of a
gall.
A special type of abnormality, of a rather distinct kind and which may be classified with
organoid galls, is fasciation. These are cases, where a normally cylindrical or radially
symmetrical plant part becomes flattened and elliptical in cross section to form ribbon like
sometimes ring-like structures.
3. Plant Gall Research work done in India and elsewhere:
Man’s knowledge of plant- galls dates back to 17th century. Greek Philosophers like
Hippocrates, Theophrastus, Pliny and others have called attention to the plant galls from the
pharmacological stand point. In Europe, the scientific study of galls began with Marcello
Malpighi who published a book, De Gallis in1686. Later, many naturalists like Kuster, Cosens,
Cook, Wells, Kendell, Houard, Hough and others contributed wealth of information to enrich our
knowledge of plant galls.In India, Prof. M.S.Mani initiated the scientific studies on galls which
paved way for many researchers to undertake the cecidological research for Ph. D, degree. Two
monographs published by Mani, (Ecology of plant galls, 1964. Plant galls of India, 2000) are time
honoured treatise on cecidological science.
3.1 Biochemical aspects of plant galls:
Galls were well known to the ancient writers and pliny records the use of their infusion as a test
for sulphate of iron in verdigris, possibly the earliest mention of an attempt to detect
adulteration by chemical means. Throughout history, galls have played a part in the affairs of
man. In medieval times, plant galls were used as medicines and for dye stuffs, and subject of
much superstition and folklore. In the recent past, the galls have been important commercial
commodities used industrially as a source of tannins and ink production (Williams, 1994).
In addition to the above recorded information there is a great wealth of knowledge concerning
the medicinal, narcotic and other properties of plant galls that is still transmitted orally from
generation to generation by tribal societies. The use of modern isolation techniques and
pharmacological testing procedure means that new plant galls (phytodrugs) usually find their
way into medicine as purified substances rather than in the form of galenical preparations. In
recent years there has been an immense revival in interest in the herbal and ISM all of which
rely heavily on plant sources. It was stated that the current return of phytotherapy was clearly
reflected by the increased market of such products. In response to the increasing prominence of
herbal remedies additional contributions describing scientific investigation of a rigorous nature
are welcomed. Phytochemical studies of galls are limited and the knowledge of the physiology of
the galls is inadequate. Rarely, galls are used as a source of tannic acid. Tannic acid is used as
an astringent and styptic. Pharmaceutical tannin is prepared from oak galls and yields glucose
Organisms and Environment
184
and gallic acid on hydrolysis; many commercial samples contain some free gallic acid (Trease et
al, 1976). Undoubtedly, the plant kingdom still holds many species of plant galls containing
substances of medicinal value which have yet to be discovered; large numbers of plants are
constantly being screened for their possible pharmacological value.
Nutritional Biochemistry is an important branch of Biochemistry from practical consideration
and for guidance to offer “Health for All”. Malnutrition among human population is a thorny
problem which has been engaged the attention of the WHO from its very inception. The
nutraceutics concentrates of galls properly prepared would offer a good source of vitamin,
minerals, carbohydrates etc. Suitable methods have to be worked out for the actual manufacture
of the concentrate.
3.2 Review of Biochemical Dynamics of Galls:
Plants are known to release localized and systemic signals in response to wounding by
phytophagous insects. Systematic induction of resistance implies the production of a signal
being translocated to the other parts of the plant where it induces defense
mechanisms.Chemical ecology is concerned with communication of signals through specific
chemical between organisms in an ecosystem (Green blatt et al, 1983). It has become dominant
in understanding of insect plant interactions. Signalling chemicals that an organism can detect
in its environmental and which may affect the organisms behaviour or physiology are called
semiochemicals. Those that act between members of the same species are called pheromones,
and those that act between species are called allelochemics. Plants are known to produce a wide
variety of allelochemicals that influence plant-insect relationships.
Ananthakrishnan (2002) stated that recognition of plant allelochemicals as agents influencing
the behaviour of insects and their natural enemies is comparatively recent. The green leafy
odours of plants comprising mixtures of fatty acid derivatives such as C6 aldehydes, alcohol and
esters provided by the lipoxygenase pathway forming “aerial bouquets” enable insect to reliably
detect host plants through olfaction. Many of these plant volatiles also stimulate oviposition, and
oviposition deterrent substances are important aspects deserving increased consideration. This
reliability and detectability of volatile chemical stimuli from the first to the second trophic levels
assume considerable significance. Suggestion has also been made that insects inject plasmid
and viroids into the plant genome and take over gene regulation to produce gall (Cornell, 1987;
Weis, 1986).
Hori (1992) reported that Indole Acetic Acid (IAA) in the saliva of the insects is considered to be
an “inducer” of galls. “Cell conditioning” precedes gall induction. Polyphenol oxidase (PPO) is a
component of the saliva of the insects and PPO phenolic compounds increase in plant tissues
attacked by insects. The complex role of phenolic compounds and phenol oxidases may indicate
that plant-PPO system has a more fundamental significance in gall production.
Rohfritsch (2006) has explained the phenomenon of induction of galls stating that insects only
cause wound to the plant tissue during feeding and then in wounded plant cells several
molecules (Unknown presently) could become active, which in turn activate the cells around the
wounded site and such an action results in the initiation of galls.
The growth promoters such as auxins and cytokinins stimulate the abnormal growth in tissues.
Two hypotheses explain the auxin theory of gall growth.Hartley (1999) hypothesized that
accumulation of phenolic compounds in insect-attacked tissue promotes cell divisions by
interacting with available IAA and/or IAA oxidases other chemical signals, specific to particular
gall-host plant system, may also play a role. On the other hand, Miles hypothesis (1999)
explains that use of oxygen in plant tissue under insect attack may be so intense that IAA
oxidase activity, which regulates syntheses and accumulation of IAA, is deprived of adequate
oxygen supply and this enables the accumulation of IAA, which in turn triggers plant-tissue
growth. Extractable constitutents of commercially important cynipid caused oak galls are
reported to contain 44 – 70 % tannin. Galls are known to have been dried and crushed to a
powder for preparing pigment used in tannin – based or gall iron inks (Lehner, 1926).
3.3 Food galls:
ISBN: 978-93-89808-99-5
185
An aquatic grass, Zizania latifolia (Poaceae), when infected by a smut fungus, Ustilago esculenta
develop a fleshy edible gall possessing unique flavors and delicacy.This gall is used as vegetable
in Taiwan, South Korea and Manipal in India.
Houard has listed nearly 3,200 galls of Angiopserms from Asia, Africa, Australia and about 300
galls from South America. In 1911, Kuster listed over 5,500 galls in Angiopserms. Ross &
Hedicke 2,900 galls on the plants from Europe alone. Mani (2000) has recorded 760 gall from
India. These galls are distributed over 87 angiosperm families and 424 species. Jayaraman
(1989) has contributed to the discovery of many more new galls. Amerjothy (2005) has enriched,
thus list by adding 180 galls caused by various causative organisms, mainly from the semi-arid
forests of South Indian. The total number of galls so far known from all over the world is
certainly not less than 1, 4750. This number is by no means final, because new records and
reports of galls are being published time and again. When compared to the bulk of galls hitherto
recorded and the great complexity and range of morphological and organizational variability of
these abnormal outgrowths, not even a fragment of these galls have been investigated in
anatomical parameter. During the present study we have recorded 9 new remarkable galls. With
these perspectives in mind, a few selected host plants associated with galls have been chosen for
the present study. The plants include different growth habits of herbs, shrubs and trees, which
are in natural habitation with little human interference. Though, plant galls have been
botanically recorded, much less studied for phytochemistry and nutraceutic values. The plant
gall study also embraces new dimensions i.e. phytochemistry and nutraceutic concentration of
galls. The plant gall work may help in the development of a nutritional security system designed
to ensure to get some nutritive compounds from galls.
Ø Nutraceutical Value:
Although it is well known that the induction of insect galls involves a species specific
manipulation of host plant anatomy (Meyer and Maresquelle, 1983), it also appears that the
physiological attributes of galls include either a reduction or increase of nutrients used by the
growing tissues of the gall or the insects within. Even though galls are atypical plant organs, it
is assumed that mineral nutrients are used no differently than they are in normal plant
metabolism (Rohfritsch and Shorthouse, 1982). Thus the ability of galls to act as physiological
sinks for various minerals reflects the galls metabolic need for the various elements.The plant
galls have not gained as much popularity as other vegetatives in the food and neutraceutics
arena. Many galls, especially certain smut fungal galls have folklore claims for food values.
Ø Dye:
Many galls develop bright pigmentation of red, brown, purple and yellow hues (eg. Terminalia
chebula). Many trees bear huge and massive galls which are rich in tannin and pigmented with
various colours. The gall-biomass can be subjected to extract dyes. The study of dye-yielding
potentials of the plant-galls is a thrust area of rewarding results.
Ø Phytochemical estimation of galls:
It is well known that many secondary metabolites synthesized elsewhere in a plant, are
irreversibly shunted to the galls where they sink in different tissue zones. Many galls are found
to be rich in proteins, tannins and calcium oxalate crystals. The overall estimation of qualitative
phytochemical analyses of chemical compounds in the galls and their corresponding organs are
also aimed in the present investigation. The chemical analyses of the gall tissues with respect to
bioactive properties remain a virgin area of study. A preliminary account of phytochemical
investigations is highlighted for 10 galls in the present study.
4.Gall inciting guild of cecidozoa:
Phytophagous Insects and Mites, though feed on the plants, all of them do not have the
potentials for inciting the galls. Only selected groups have evolved the cecidogenetic skill. Table
1, shows different groups of the insects and mites that produce galls in the shola forests. Of
other cecidozoa, the members of Diptera, especially cecidomyhiidae (Gall–midges) outnumber of
other groups of insects. About 37 % of galls are incited by the Dipteran insects. This fact is not
only true to the Shola Forests of South India, but also to whole of India as well as to the world
flora (Mani, 1973).
Organisms and Environment
186
Several factors can be attributed to the gall–midges for their predominance of gall inducing traits
(37%). The gall midges generally possess well-developed salivary apparatus. The gall midges can
feed on wide range of plant organs from apical bud to hard stem. The gall midges seem to
possess adaptability to thrive in a wide range of ecological ambience. We reared and identified
the gall-insects and mites.
Table 1. Gall insect index & their gall frequency
S.No.
Causative organisms
No. of Plants
1.
Midge – Diptera
47 (37%)
2.
Mite (Acarina, Eriophyes)
33 (26%)
3.
Psyllid (Homoptera)
18 (14.1%)
4.
Thrips (Thysanoptera)
14 (11%)
5.
Fungi
6 (4.7%)
6.
Weevil (Coleoptera)
4 (3.2%)
7.
Moth (Lepidoptera)
2 (1.6%)
8.
Unknown agent
2 (1.6%)
9.
Bacteria
1 (0.8%)
Total
127 (100%)
The galls in the Shola Forests are caused by diversified taxonomic groups of animals, parasites,
especially insects and mites. They feed on the plant tissues; however, all of them do not have
the potential for inciting galls. Only selected groups have evolved the skill to induce galls.The
important cecidozoa are briefly accounted below.
The eriophyid mites (Acarina: Eriophyidae) are microscopic, wingless organisms with t wo pairs of
legs and elongate cylindrical body; the mites may be white, yellowish-red or brown. They are
usually 80 – 280 mm long. The mouth parts of the eriophyid mites are adapted for boring single
cells with the help of the needle shaped mandibles and suck the cell contents in liquid form.
The eriophyids have remarkably large salivary glands and the salivary secretion is injected into
the plant cells while they injest the contents at the time of feeding.
The principle gall inciting insects fall under Thysanoptera, Homoptera, Coleoptera, Lepidoptera
and Diptera. Certain insects have been reported to cause galls by thrusting their eggs into the
plant tissues, thereby the surrounding cells are rendered hypertophy to develop into what is
known as procecidia (Mani, 1964). However, most of the galls are initiated by the feeding activity
of the larva or both larva and adult insects as in the cases of Thysanoptera and Homoptera.
4.1 Thysanoptera:
The gall thrips constitute an important group of cecidozoa. According to Ananthakrishnan
(1981) nearly 300 species of thrips genera are associated with galls. In the scrub forests, the
thrips galls represent one of the dominant types. The thrips induce galls mostly on leaves, in
which the marginal meristematic activity has just ceased and laminar expansion has started.
The thrips feed on the epidermal and sometimes also on the subepidermal cells by “punch and
suck” feeding mechanism. Repeated wounding and continued feeding on a large area of the host
leaf seem to be essential for effective development of the gall. The thrips galls are simple in
external form which is attributed to gall induction during late stage of leaf ontogeny
(Ananthakrishnan, 1980).
4.2 Homoptera:
This order includes many important gall insects which belong to the families Chermidae
(/Psyllidae), Aphididae, Phylloxeridae, Aleurodidae and Coccoidae.Of all these groups, the
psyllids constitute major group of insects responsible for the shola forest galls. They induce
galls on the leaves and the galls are mostly pouch type or pouch-cum-covering-growth type.
4.3 Coleoptera:
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Weevils, the principal gall forming group of Coleoptera, are hard bodied insects they have biting
and chewing mouth-parts. The female weevils, using the snout, scoop cavities in the plant
organs into which they thrust their eggs. As the larva emerging from the eggs feed on the
surrounding tissues, the gall initiation takes place. The weevil galls mostly occur on the tender
stem, petiole and midrib.
4.4 Lepidoptera:
The Lepidoptera insects are commonly known as moths. The common caterpillars are the larvae
of the Lepidoptera; some of the caterpillars are potential gall-formers in the shola forests. The
moths lay eggs always on the surface of the tender plant organs such as shoot axis or
occasionally on the buds, but never within the plant tissues. The newly hatched larvae bore
their way into the tissues, so that the larvae are eventually burried inside the plant organs. The
larva has biting and chewing mouth parts; they are fairly large and occupy more or less entire
gall cavity; within the gall the caterpillar is usually in vertical posture and show slight forward
and backward movements. In the apical bud galls, the adult moth escapes through wide,
circular apical pore; in the internodal galls, the moth makes a hole on the lateral walls of the gall
cavity through they escape. In certain galls, the gall splits longitudinally along four or more
lines; the slits thus formed allow the moths to leave the gall.
4.5 Diptera:
The Diptera represents the most dominant gall insects not only in the shola-forests but also
through out the world. The Dipteran gall insects fall under Cecidomyiidae, Agromyzidae,
Trypeptidae and Authomyidae.Among these groups, the cecidomyiidae includes the maximum
number of gall inciting species. The cecidomyiid midges owe not only to the highest number of
galls but also to more complex and remarkable galls. The Dipteran insects attack any aerial
organ of the plant. They lay eggs either on the plant surface or within the tissues. The larvae
coming out of the eggs are yellow or yellowish-orange. With the biting and chewing mouth parts
the larvae feed on the tissues and incite the gall. Several unique morphogenetic processes are
involved in the ontogeny of the Diptera galls. Fusion of tissues, coordinated growth of two
organs to form a complex gall, curious shape and alluring ornamentation are met with the
Dipteran galls.
4.6 Fungi:
Gall inducing fungi occur in certain major groups, causing galls on both domestic as well as wild
plants. The gall inducing fungal parasites come under Plasmodioph- oromycetes,
Chytridiomycetes, Oomycetes, Homobasidiomycetes, and Ascomycetes. The fungal galls
generally assume unlimited size and amorphous appearance because of the virtue of the fungal
organisms permeating wider host tissues rendering them to undergo diffuse proliferation.
· Association of fungal flora in the galls:
In many galls induced by mites and insects fungal mycelium is seen inside the gall cavity. In
Ipomea staphylina, the gall induced by Asphondylia ipomea, is constantly found to harbour well
determined fungus in the gall cavity. In a fruit gall of indegofera asplathoides caused by a midge,
a fungus mycelium is found to occupy the entire gall cavity. Krishnamoorthy and Raman (1972)
reported some fungus occurring intercellulary inside the gall cavity of Aeachynanthea perrottetii
caused by a midge. Felt (1965) says that is ‘ambrosia galls’ there exists a definite relationship
between the gall midge and the ambrosia fungus. In European galls caused by Asphodylia and
Lesioptera ambrosia has been observed quite commonly. The relation of the gall midge larva in
the fungus and the part the latter plays, if any, in the development of the gall are worthy of
investigation neither the taxonomy nor the nature of association of the fungi found in the insect
and mite galls has been given proper attention. In some cases, the insect larva which induces
the gall is reported to feed over the spores of the fungus which grows is the gall cavity (Mani,
1973). However in the present investigation it is observed that the galling agent appears first on
the host and prepares a sort of base for the infection of the microflora. Later the invader seems
to be parasite over the gall maker. This appears to be the case at least in the galls on Ipomoea
styphilina caused by Asphondylia ipomaeae. It is suspected that the situation in
Haphalophragmium on Acacia leucophloea (Thirumalachari, 1941) is similar.
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4.7 Bacteria:
The bacterial galls can be categorised into two types: i) Crown gall and ii) Bacterial nodules.
The crown gall is pathological and causes harm to the host plant. The ‘crown-gall’ of bacterial
origin was studied very intensively because of some similarities between the human cancer and
the crown gall. The nodules are of symbiotic association and of useful to the plants.
5. Alluring Spectrum of Plant-galls:
Semiarid scrub forests, though trivial in their vegetational profile, occupy a significant posit ion
in the geography of Deccan plateau and Eastern Ghats. This ecoregion is neither exceptionally
species rich nor high in endemism, because metereologically the forests experience feeble annual
rainfall, high atmospheric temperature and low humidity. However, the ecosystem complex of
the scrub forests is alluring both in its magnitude and complexity. This is very much exemplified
by the insect-plant association prevailing in the scrub forests. The gamut of variation of the
insect-plant interactions ranges from simple phytophagism to the most complex system of
balanced parasitism on the insect side and self-defense adaptive strategies on the host-plant
side.
In a comprehensive survey of plant-galls, we were able to record in the South Indian Scrub
forests several remarkable galls of excelling architectural designs and sublime marvels. A few
such illustrious galls are highlighted here.Certain gall-midges (Lobopteromyia Spp.) seem to have
evolved an inbuilt dexterity to involve two consecutive leaflets of Acacia spp. and to mould
complementary galls which surprisingly fit in with each other. Eg: “hour-glass shaped gall” and
“cylinder and piston” gall on Acacia feruginea, “cup and saucer gall” on Acacia catechu and
Acacia chundra. A guild of Asphondylia spp. have developed handiness to formulate gall within
the young folded lamina and to inhibit the leaf to unfold either by grafting the leaf tissues (Eg:
Rivea hypocrateriformis) or by bridging the lamina through a gall (Eg: Ipomaea staphyllina). An
unknown gall midge indiscriminately infests all aerial parts of Zizyphus xylopyrous to incite
curious beaked-bowl gall”. On Garuga pinnata a psyllid, Phacopteran leutiginosum builds a
wide, circular copular erupting structure from which a cylindrical, hollow bright red secondary
body is produced.
The phytophagous mites lag least behind the insects in cecidogenetic potentials. A mite,
Eriophyes dichrostachia bridges two successive leaflets of Dichrostachys cinerea by a barrel
shaped gall. Another aggressive mite infests entire compound leaf of Acacia concinna and turns
in to brightly coloured amorphous body of deformed leaflets. These galls and many more galls
are strictly endemic to the South Indian Scrub forests. The gall diversity and their pronounced
endemism in relation to the Ecosystem are discussed.
5.1 Cup-saucer leaf gall of Acacia catechu Willd. by Lobopteromyia bivalviae (Rao) Mani
Host: Acacia catechu Willd. (Family-Mimosoideae): Thorny tree of scrub forests.
Gall Forming Agent: Lobopteromyia bivalviae (Rao) Mani (Diptera)
Gall morphology (Fig. 1, 6): Complex gall involving two or more consecutive leaflets of the same
side. Gall Reddish brown, conspicuously visible eye catching remarkable gall. The gall develops
between anterior and posterior leaflets. The anterior leaflet develops into abaxially concave cup-
like body while the posterior leaflet forms plano-convex, adaxially flat structure. The anterior
cup and the posterior saucer-shaped part fit accurately with each other forming a gall complex
called “cup-sacuer” gall. The midge larva lies inbetween the cup and the saucer.
Anatomy of the gall (Fig. 2): Induced by the larva lying inbetween two consecutive leaflets, the
mesophyll tissues of the anterior and posterior leaflets undergo initial hypertrophy followed by
cell divisions in periclinal plane. The anterior leaflet undergoes increased proliferation of the
upper part of the tissue, so that it becomes curved abaxially; the upper part of the lower leaflet
also proliferated more profusely forming a flat platform towards the curved anterior leaflet. The
mature gall has arcs of sclereids (sclerotic zone) both in the upper and lower galls; the gall cavity
is lined by a few layers of cells; the outer portions of the galls have vertically stretched compact
parenchyma cells.
Locality: Karnataka; Scrub forests of Tamil Nadu, rare;
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Ref.: Jayaraman,1983;Mani,2000.
5.2 Leaflet arced-gall of Acacia chundra (Roxb. ex Rottl.) Willd By Lobopteromyia sp.
Host: Acacia chundra (Roxb. ex Rottl.) Willd (Family-Mimosoideae): Stragling shrub.
Gall Forming Agent: Lobopteromyia sp. (Diptera)
Gall morphology : Complex gall involving two or more consecutive leaflets. The gall strikingly
simulate the “cup-saucer” gall on Acacia catechu. The consecutive leaflets harbour the larva
inbetween the narrow gap; the anterior and posterior leaflets develop into an arc shaped gall
with abaxial concavity. The arced leaflet galls fit in with each other in such a way that the
anterior gall is incubous over the posterior gall. The apical part of the leaflets remains normal
and appears as beak. The gall is green, smooth, indehiscent and the colour does not change
even after maturity. A bipinnate compound leaf has almost all the leaflets turned in to galls.
Locality: Thirupathi foot hills. Not common; new record.
5.3 Cylinder-piston gall of Acacia ferruginea DC. by Lobopteromyia sp.
Host: Acacia ferruginea DC (Family-Mimosoideae): Small thorny tree.
Gall Forming Agent: Lobopteromyia sp. (Diptera)
Morphology of the gall: Complex gall with remarkable profile and colour; formed by
coordinated growth of two successive leaflets of the same side, appearing as complex of
“cylinder-piston”. The posterior leaflet produces a hypophyllous, hollow cylindrical outpocketing;
the anterior leaflet produces a solid, cylindrical rod shaped piston; the piston fits tightly into the
hollow cylinder. The tip of the cylinder has a hollow beak in which the gall-larva lives. The gall
is indehiscent, varies in colour from yellowish green to red or violet; the gall surface is smooth.
Anatomy of the gall (Fig. 3): The gall-system consists of a solid cylinder penetrating into a
hollow piston. The cylinder has compact, vertically stretched central parenchymatous tissue and
outer sclerenchymatous zone. The cylinder is derived from downward growth of the mesophyll
tissues. The piston has inner epidermis followed by parenchyma zone and outer sclerotic zone.
The terminal portion of piston is prolonged into a beak which is partly sclerenchymatic. The
larva is nurtured by the hollow cylindrical gall.
Locality: Eastern Ghats – scrub forests, not common.
Ref.: Mani, 2000.
5.4 Hour-glass gall of Acacia ferruginea DC by Lobopteromyia ramachandrani Mani
Host: Acacia ferruginea DC (Family-Mimosoideae): Small thorny tree.
Gall Forming Agent: Lobopteromyia ramachandrani Mani (Diptera)
Morphology of the gall (Fig. 6):A remarkable, barrel shaped or ‘hour-glass shaped’ gall involving
two successive leaflets. Each gall consists of two units, one formed by abaxial growth of the
anterior leaflet, another by the adaxial growth of the posterior leaflet. On the upper side of the
leaflet develops a hollow, barrel shaped, stout thick walled covering growth; from the lower side
of the leaflet lying above the lower leaflet, gives rise to a short, stumpy, cylindrical pestle-like gall
which goes into the barrel and fits exactly with the cavity. These two units form a combined
gall-complex resembling the “hour-glass”. A curved beak is usually formed on the upper part of
the barrel-gall. The gall is unilocular, hard, indehiscent, red or brown, 3 – 4 mm long and 2.5
mm thick. The gall harbours the larva in the chamber of the peg and barrel. Several galls occur
in longitudinal series on either side of the leaf.
Anatomy of the gall : The anterior cylinder consists of a broad expanded upper portion which
becomes narrowed into a solid thick cylinder below. The cylinder consists of compact, vertically
stretched parenchymatous cells with dense tannin contents. The lower portion is a wide hollow
and deep cup. The lower part also consists of parenchymatous compact thin walled cells.
Locality: Scrub forests of Eastern Ghats, not common; seasonal in occurrence.
Ref.: Mani,2000.
5.5 Cauliflorous gall of Acacia sinuata (Lour.) Merr. by Eriophyes sp.
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Host: Acacia sinuata (Lour.) Merr. (Family-Mimosoideae):Straggling shrub.
Gall Forming Agent: Eriophyes sp. (Acarina)
Morphology of the gall : Foliar gall; several leaflets of a pinna or entire leaf with almost all
leaflets are infested and turned into irregular, tuberculate, highly convoluted irregular mass; the
gall, when young, is pale green and turns brickred when old; the leaflets lose their identity and
get agglomerated into a mass. The gall mass is a fusion of several deformed leaflets.
Locality: Thirupathy foot hills ; New record; not common.
5.6 Leaflet bridge gall of Dichrostachys cinerea (L.) wight & Arn. By Eriophyes dichrostachia
Tuck.
Host: Dichrostachys cinerea (L.) wight & Arn. (Family-Mimosoideae):Small tree in scrub forests.
Gall Forming Agent: Eriophyes dichrostachia Tuck. (Eriophyes)
Morphology of the gall : Leaflet-gall; remarkable complex gall involving two or more consecutive
leaflets of the same side getting fused with the abaxial side of the anterior leaflet and adaxial
side of the posterior leaflet. A wide cavity is formed between the fused leaflets where a colony of
mites live and feed. Galls are yellow, pink, brown, circular and shortly cylindrical, form a bridge
between the leaflets.
Anatomy of the gall :The two leaflets are fused with each other through a circular zone of
elongated cells; these cells arising from the epidermal layers of the leaflets dovetail with each
other and get grafted.The upper and lower parts of the leaflets have undifferentiated mesophyll
tissue; the epidermal layers bordering the gall chamber have dense cytoplasm which s erve as the
feeding site of the mites, the free ends of the leaflets that are not involved in galling are normal
in structure.
Locality: Common and abundant.
Ref.: Mani, 2000.
5.7 Cupular covering growth rostrate pouch of Garuga pinnata Roxb. By
Phacopteron lentiginosum Buckton
Host: Garuga pinnata Roxb. (Family-Burseraceae): Large deciduous tree.
Gall Forming Agent: Phacopteron lentiginosum Buckton (Homoptera)
Morphology of the gall (Fig.6): Leaf-gall; A remarkably curious gall, alluring in size, shape and
colour. Gall occurs mostly at the basal part of the leaflet, near the veins. Epiphyllous, densely
clustered or solitary, ovoid, or sub-cylindrical, smooth, soft, hollow and apically nipple-like
mucronate. The gall consists of a basal cuplike covering growth; from the basal cup arises the
erect cylindrical part, which is constricted into neck at the place of insertion. Gall is yellow
when young, turns reddish and finally brightly reddish brown. Wide gall contains Psyllid
nymphs and adults; mature gall dehisces along the vertical cylinder. Mature galls are 2 cm high
and 1 cm thick.
Anatomy of the gall (Fig. 4):The normal leaflet has prominently projecting veins, thick and
broad epidermal layers and dorsiventral mesophyll tissues. The larval chamber is found deeply
burried in the spongy mesophyll zone; a broad massive hemispherical gall develops on the
adaxial side of the lamina above the region of the larval chamber. The mature gall has a wide
circular thick copular covering growth in the center of which a long cylindrical, fleshy,
mucranate pouch is situated. The vertical pouch has wide longitudinal axial passage where
fungal mycelium and other predators and inquiline enter as the gall attains full growth. Both
cup and pouch have soft, thin walled parenchymatous tissues. The larval chamber is seen at
the base of the cylindrical pouch and the insect seems to escape through abaxial exit hole.
Locality: Pachamalai, Yelagiri, Rare.
Ref.: Mani, 2000.
5.8 Covercone bridging gall of Ipomoea staphyllina Roem. & Schultes by Asphondylia
ipomaeae Felt:
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Host: Ipomoea staphyllina Roem. & Schultes (Family-Convolvulaceae):Straggling shrub,
abundant in the waste places.
Gall Forming Agent: Asphondylia ipomaeae Felt (Diptera)
Morphology of the gall : It is a remarkable gall of curious shape and origin. The major part of
the gall is the thick fleshy covering growth from one adaxial side of the lamina and a small
cushion of outgrowth from the opposite of the other half of the leaf. The cover-cone and the
cushion-growth develop between the folded leaf blade; the mouth of the cover-cone is tightly
plugged by the cushion like outgrowth and get grafted each other. A series of cover-cone
plugged with cushions occur along the median longitudinal line, so that the leaf remains
permenantly folded along adaxial midrib.
Anatomy of the gall: The gall consists of soft, thin walled parenchymatous tissue with profuse
vascular strands derived from the lamina. Fungal mycelium densely fills the gall chamber even
when the larva is present in the gall.
Locality: Kavaloor foot hill. Common.
5.9 Leaf fold gall of Rivea hypocrateriformis Choisy by Asphondylia riveae Mani :
Host: Rivea hypocrateriformis Choisy (Family-Convolvulaceae): Twining shrub.
Gall Forming Agent: Asphondylia ipomaeae Felt (Diptera)
Morphology of the gall :Leaf fold gall with median grafting of the folded inner part of the
lamina. The folded and fused leaf develops ovoid or biconvex gall along the median portion, the
leaf-margins being free. The gall is soft, spongy indehiscent, solitary and yellowish green.
Anatomy of the gall: In vertical sectional view, the gall has several fused points in vertical
series, with small larval chambers inbetween the sutured places. The gall has thin
parenchymatous compact tissue with reduced ramifying vascular strands.
Locality: Narthamalai. Common.
5.10 Cover cone gall of Ziziphus xylopyrus Willd. (Rhamnaceae) by Cecidomyiidae
Host: Ziziphus xylopyrus Willd. (Family-Rhamnaceae): Small tree predominant in scrub forests,
wood and fruits useful.
Gall Forming Agent: Cecidomyiidae (Diptera)
Morphology of the gall : Foliar gall – perfoliate – cover cone gall consisting of funnel shaped
adaxial growth and beaked cone on the abaxial side; walls of the gall thin and brittle; gall
chamber wide, smooth, gall surface sparsely hairy, greenish yellow. Stem and fruit galls are
sharply beaked cover cone gall with wide even larval chamber leading to apical operculum.
Anatomy of the gall: Both foliar and stem/fruit galls have compact parenchymatous tissue.
Distinct nutritive or sclerotic zones are lacking.
Locality: Orakkadam. Common.
6. Grafting and tissues fusion in galls:
Union of cells or fusion of tissues similar to the process that occurs in grafting of tissues has
been observed in a few galls. In Rivea hypocrateriformis and Ipomea styphylina both attacked by
two different species of Asphondylia, we come across a sort of grafting or union of cells in the
gall. In Ipomea syphylina a cup like outgrowth develops from one of the inner sides of the young
folded lamina, and from the opposite a plug of tissue appears which grows and fits into the
opening of the cup of the opposite lamina. Later, the cells of the plug and the rim of the cup
undergo cell union, so that the two halves of the lamina remain bridged by the galls even at
maturity. In Rivea hypocrateriformis also the young folded lamina undergoes cell union at one or
more places during origin of the gall. In the mite gall on Dichrostachya induce by Eriophyes
dichrostachise a single type of cell union is seen between the interlocking epidermal hairs of the
opposite leaflets. In the above mentioned instances, union of cells may be considered as a simple
type of grafting. In the galls, the grafting involves a simple attachment of surface layer of cells
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by cuticular layers, whereas in the grafting of agricultural practices a kind of organic connection
is established by formation of vascular strands between the stock and scion.
7. Polarity of morphogenesis:
Establishment of histological, histochemical and functional polarity has been recognized in the
morphogenesis of plant organs and tissues. This is an essential feature in any orderly
development which results in an organ of definite shape and size. Furthermore, polarity is found
to be a basic feature of any living cell or organism, such a feature being manifested even at the
unicellular of an organism. Under suitable conditions, cells or tissues may manifest their
polarity is normal way or it may be modified by any external organism. In many plant galls of
prosoplasma type, such as organized form and size is established only through well determined
morphogentic polarity while in the pouch galls of mites and insects, the polarity of cell divisions
is at right angles to the surface of the organs, later this is followed by lateral expansion. In
pouch galls with covering growth, the lower half of the gall elongates vertically and matures in to
long narrow cells at right angles to the surface. Thus, these few instances are indicative of a
replacement of the original polarity by an altered one.
8. Phenomenon of wound healing in gall:
Wound healing is a natural phenomenon found in all groups of plants. A wound made either by
experimental or natural means is healed by formation of callus from the intact cells around the
destroyed cells of the wound. The cells of the wound tissue are elongated at right angled to the
wound surface and they divide in periclinal plane to form a radial seriation of cells. In a
wounded tissue, a gradient and reactivity becomes established from the margin of the wound
towards the centre, the deeper cells showing higher degree of meristematic activity than the
cells on the wounded surface. The usual traumatic responses include sclerification of living
cells, redifferentiations of tracheary elements from parenchyma cells and cytological
modifications of the wound cells (Bloch,1941; Bloch,1952; Swamy et al, 1972; Swamy et al,
1975). Many gall insects make conspicuous wounds on the plant organs either during entry of
the larva or in feeding activity. Larva of most Diptera, Lepidoptera and Coleoptera possess biting
and chewing type of mouth parts and they make wounds to get their nutrition. The presence of
wounding in the case of gall insects involves not only damage of cells and liberation of the
contents of the broken down cells, but also salivary secretions of the feeding larva (Miles, 1968).
Furthermore, the wounding here is not haphazard. It is made at a specific place of the plant, in
a specific stage of saturation of the host tissue and in a specific mechanism by the insects. In
the case of insect injuries, they are made constantly, but in lower degrees. These differences
account for certain variations in the general processes of wound healing in nature and in
cecidogeny. Cook (1902), who made intensive studies on the morphology of several types of galls
and the structure of mouth parts and ovipositor of the insects concerned, concluded that the
response of the host tissues to develop into gall is a continuous effect of the plant to heal the
wound made by the insects. In the present investigation, conspicuous wounding is observed in
the vein galls of Achyrathes aspera, Ficus religiosa and Odina wodier. In the stem galls of
Carissa spinarum, Coccinia indica and Memordica charantia all caused by midges. In the
Lepidopterous galls of Carissa sepiaria, Emblica officinalis and Tephrosia purpuria, tropical
wound is made on the host tissues by the larva. In all these cases, the general histological and
anatomical responses are somewhat similar to those resulting from natural wounding. The
intact cells around the wound become hypertrophied and subsequently divide by periclinal walls
to produces a radial seriation of cells at right angles to the wound surface. These cells have
prominent nuclei and exhibit some nuclear abnormalities. These are typical wound healing
processes resembling those observed in experimental studies on wounds (Swamy and
Sivaramakrishnan,1972, Sivaramakrishnan, 1975). Surgical experiment on plant tissues
conducted by investigators (Bloch, 1944, Roberts et al. 1962, Cutter, 1972) showed that the
sclereids and xylem elements differentiate from parenchyma cells somewhere away from the
wound. In some of the galls studied at present, viz., Coccinia indica stem gall induced by
Neolasioptera cephalandrae, Cordia myxa, petiole gall induced by Baris cordiae, Odina wodier
vein and rachis gall induced by Lobpteromia vivalviae, a distinct sclerotic zone appears
somewhere away from the wound around the larval cavity. In all these cases, the development
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of sclereids may be partly due to the wound healing effects, even though some other factors may
also be involved in the process. However, in certain galls, such as vivalved gall on Acacia
catechu induced by Lobopteromyia bivalviae and leaf fold gall of Rivea hypograteriformis induced
by Aspondylia riveae no conspicuous wound is found, yet sclerenchyma zone is formed to Acacia
catechu while it is absent in Rivea hypograteriformis. The actual phenomenon of induction of
sclereid formation is Acacia catechu and its absence in a similar situation in Rivea
hypograteriformis remains to be clarified.
9. Nature of the cecidogentic stimulus:
The nature of the stimulus that operates in the origin and development of galls has been the
subject of controversy for a long time. The problem was initiated during the period of Malphighi
(1628-1694) and still now it parasites drawing the attention of almost all students of cecidology.
The nature of the stimulus is considered to be either mechanical (Cook, 1902) or chemical
arising from the larva (Miles, 1968) or from the associated microorganisms (Hough, 1960).
The gall insects belonging to Homoptera, Lepidoptera and Diptera make mechanical injury on
plant tissues to derive the nutrition. Such injuries cause development of wound tissues as a
response to the healing of the injuries. In the formation of wound callus tissue, mechanical
injury is only an insignificant element in the chain factors. A large number of chemicals have
been reported to be ontogenic (Arya et al, 1975). However, the chemical galls are characterized
by their limited hyperplasy and none of the carcinogens give rise to galls cooperable to those
incited by biological agents. Salivary enzymes of cecidozoa with specific gall forming principles or
cecidotoxin are associated with the galls (Mani,1964; Miles,1968). The host plants react to the
cecidotoxin in highly specific and specialized way and not every plant or every part exhibits this
reaction always. From the present investigations one is inclined to formulate that the
cecidogentic stimulus is complex in nature, consisting of mechanical injury, specific cecidotoxin
and specialized reaction of the host plant. In a given type of gall all these factors may operate
equally and simultaneously or any one may take the upper hand. In specialized galls, such as
Lobopteromia gall on Acacia catechu, the nature of the stimulus seems to be more of
physiological than of physical or chemical. The facts hitherto discussed are based on anatomical
and ontogentic studies of a few representative galls. Those facts are to be supplemented by
further studies on cytology and histochemistry of these strange neoplastic growths – a field of
great promise for future investigations.
Conclusion:
Galls are plant excrescences induced by the action of specific groups of Insecta and Acarina,
which manifest as neoformed structures. Insect induced galls are beautiful objects sculpted by
Nature (Raman, 2018). We require a character - a special one – to admire the beauty of these
natural sculptures. It needs to be mentioned here that the number of workers engaged in plant
and insect species identification in this country is significantly minimum to deal with such a
large number of species. It reveals that there are no experts in several groups and there are only
a few experts in most of the groups. This is also alarming that while large number of plant and
insect species is yet to be explored and identified, the number of experts is gradually declining.
Many of them have retired from service and other social causes. On the other hand there is no
replacement for them since taxonomic studies in the universities are discouraged. There is also
scarcity of standard taxonomic collections and institutional facilities to develop taxonomic
experts. At this juncture I wish to quote the golden words of American photographer Wilson
‘Snowflake’ Bentley’s (1835 – 1931, Jericho, Vermont) words, ‘Their (snowflakes) uniqueness is
part of their fascination and romance, yet there is undoubtedly something similar about them;
they share a ‘six-ness’. Which is more interesting? Perhaps it depends on the character of the
observers’ (in Appleton’s Popular Science Monthly, 1898). The arthropod-induced plant galls are
in no way different from what Bentley speaks about snowflakes. The plant galls are stunning
and beautiful, yet each gall type induced by an arthropod species is unique in space. According
to Raman (2018), as a rule of thumb, experienced scientists working on galls and gall inducing
arthropods can easily determine the plant by looking at the inducing organism and the gall, and
determine the inducing organism by looking at the plant and the gall. Several amateur biologist
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and hobby natural historians passionately pursue these curious sculptures, similar to others
interested in snakes and other reptiles, birds, butterflies, mushrooms and ferns.
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Organisms and Environment
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Fig. 1 : Cup and Saucer gall in Acacia
catechu W. & A. by Lobopteromyia
bivalviae (Diptera)
Fig. 2 : T. S. Cup and Saucer gall in
Acacia catechu W. & A. by Lobopteromyia
bivalviae (Diptera)
ISBN: 978-93-89808-99-5
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Fig.3: T.S. of Cylinder Piston Gall in Acacia ferruginea DC. [Mimosoideae]
Organisms and Environment
198
Fig.4 : T.S. of Cupular covering gall in Garuga pinnata Roxb. By
Phacopteron lentiginosum
ISBN: 978-93-89808-99-5
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Fig.5: Commonly occuring Plant Galls in Tamil Nadu, India
Organisms and Environment
200
Fig. 6.
F
Fig.6:Alluring spectrum of Plant galls.
