MSc 3rd Semester 2020-2021

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kanika sharma

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Dear Students I had tested positive for Covid 19 and was hospitalized so i was unable to connect with you all. but I am feeling better now. i am posting two topics. on galls; anatomy and physiology of galls. Please read the notes and ask any questions during the class. the link will be shared with you on the whats app group. I will take another week or so to take full 2 hour class as My throat is still sore, but I will be there to answer any of your queries and clear any doubts.

Anatomy of galls.doc

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Physiology of gall formation 7.9.20.doc

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General characters of Cecidogenesis.doc

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structure of Prosopis stem gall.pdf

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suraj maliOct 6

We are pray for your quick recovery mem🙏

Hemantshree RathoreOct 6

Get well soon ma'am🙂

Harshita jadonOct 6

Get well soon ma"am...🙏

Anju menariyaOct 6

Get well soon ma'am

Bhanwar PrajapatiOct 8

Get well soon mam take cure

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rohini trivedi

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Material: "Introduction to plant galls"

kanika sharma posted a new material: Introduction to plant galls

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kanika sharma

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Dear Students I am uploading the part ! of my notes on Plant Galls. Please read them and we can have an interactive session in todays class at 1.30.pm. The link to google meet will be shared with uou on the whatsapp group.

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Material: "introduction and history of Plant pathology"

rohini trivedi posted a new material: introduction and history of Plant pathology

Created Aug 7 – Deleted

Question: "1. What is relative humidity? 2. Describe in short light pollution? 3. Describe the process of acid rain ? 4. State instances in World history where plant diseases led to massive low yield and food production. 5.State instances in India where plant diseases led to massive low yield and food production. 6.How the need to control plant diseases led to indiscriminate use of chemicals (pesticides ) which led to land water and soil degradation. 7. Write the name of one disease and its pathogen with systematic positionand its diseased host which as result of infection produced poisonous and ufit substances (give the name and its effect ) on human consumption."

rohini trivedi posted a new question: 1. What is relative humidity? 2. Describe in short light pollution? 3. Describe the process of acid rain ? 4. State instances in World history where plant diseases led to massive low yield and food production. 5.State instances in India where plant diseases led to massive low yield and food production. 6.How the need to control plant diseases led to indiscriminate use of chemicals (pesticides ) which led to land water and soil degradation. 7. Write the name of one disease and its pathogen with systematic positionand its diseased host which as result of infection produced poisonous and ufit substances (give the name and its effect ) on human consumption.

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rohini trivedi

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M.Sc CBCS IIIrd Semester

Avanced Plant Pathology I (DSE1)

Unit V

Topics: Physiology of gall formation.

What you will learn?

 What metabolic changes take place in gall tissues

 Which metabolites are responsible for abnormal growth

The variation in morphological complexity is also followed by a variety of physiological traits.

Galling insects do not only control the developmental patterns of the host plant, so as to define

the gall phenotype, but also its physiology. Galls are sinks of photoassimilates. Galls may

produce photoassimilates, but in such low values that it seems improbable that they could

guarantee gall maintenance without draining resources from their host organ. The physiological

gradients inside and outside the gall tissues revealed specific enzymatic activities and are also

accompanied by cytological peculiarities .The galls function as sinks of nutrients mobilized from

the other host plant parts . A large set of evidences support that the galling insect is able to

manipulate the host plant, inducing the formation of nutritionally superior cells in comparison to

the other healthy plant tissues, the nutritive tissue. The cells of this tissue have a high

concentration of lipids, glucose, amino acids, and a high enzymatic activity, including

phosphatases, proteases, and aminopeptidases rich in RNA and ribosomal RNA of the nucleolus

(Bronner 1992). On the other hand, the parenchyma cells of the outer cortex form a reserve tissue

characterized by a high concentration of starch, low concentration of lipids and glucose, and low

enzyme activity. As the larva feeds on the cells of the nutritive tissue, there is a replacement of

substances by the cells of the reserve tissue. The translocation of substances between the two

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tissue zones has been proven to need an intense enzymatic activity. Also, the substances

accumulated may be diverse, such as proteins, carbohydrates, and lipids

The most general hypothesis suggests that gall formation is triggered by the action of chemical

substances secreted by the gall inducer, including plant growth regulators such as auxins,

cytokinins, indole-3-acetic acid (IAA), and other types of compounds. However, the mode of

action of these chemical substances and the general mechanism by which the insect could control

and manipulate plant development and physiology is still not known.

Gall formation is a defense reaction of the host plant and is related to either the feeding activity.

The prime aim of host is to restrict the proliferation and the main aim of insect is to suck

nutrients from the host. In many cases the stimulus appears to come from the saliva of the

developing larva, while in others it seems to be chemically injected during egg laying. Like

effective parasite the gall insects do not kill their hosts but they draw the resources of the host

cells for themselves. Galls restrict the injury by gall maker. Insect gets food , shelter and place to

reproduce.

Various theories exist regarding gall development and induction mechanism:

1. Insect synthesizes cecidigen (gall forming metabolite) which causes gall formation.

2. Insect stimulates plant hormones. Deranged metabolism leads to gall formation.

3. Enzymes or enzyme like secretions in insect saliva are responsible for gall induction.

For successful survival the cecidozoa utilizes two basic adaptive strategies:

 development of abnormally large cell (hyperptrophy) or excessive multiplication of cells

(hyperplasia)

 Transformation of differentiated tissues into meristematic tissues.

The cellular realignment due to hypertrophy in early stages of feeding often result in the

establishment of galls. The gall inducer exploits the resources of the host maximally by

synchronizing the time of active growth in the plant with the appearance of gall insect.

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Gall morphogenesis is a complex phenomenon, which involves reorientation of the plant’s

development by the inducing insect. The degree to which the insect manipulates the plant’s

growth to form the gall varies considerably and involves changes ranging from the induction of

cell proliferation to the formation of a complex structure that the plant does not produce under

normal conditions.

Several theories have been proposed to explain the physiology of gall formation.

1. Insect saliva alters the subcellular environment of cells and thus places it in a state of

chemical shock which induces osmotic changes. This establishes the first recognizable

stage in gall induction. Plant produced metaplasied cells to repair the wound and

neutralize the osmotic-change induced stress. Localized metabolic changes spread, from

these cells, not throughout the involved plant organ, but in a limited manner around the

immediate site of insect occurrence. The osmotic-change related stress prevails till the

insect feeds. Osmotic stress affects electrical properties of the plasma membrane and

impacts on IAA activity, which in turn, alters H + -transport systems. During the physical

action of insect feeding, the host-cell wall breaks down, and the degenerated wall

materials act as elicitors.

2. The most general hypothesis suggests that gall formation is triggered by the action of

chemical substances secreted by the gall inducer, including plant growth regulators such

as auxins, cytokinins, indole-3-acetic acid (IAA), and other types of compounds.

However, the mode of action of these chemical substances and the general mechanism

by which the insect could control and manipulate plant development and physiology is

still not known.

3. The inducing insect can modify the expression of genes within restricted areas of the host

plant, thereby producing new developmental events in the tissues under its influence.

4. Insect synthesizes and secretes cecidogen; the gall forming metabolite which induces gall

formation.

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5. The feeding /ovipositon activity stimulates the growth hormones and or cause altered

synthesysis of carbohydrates, proteins, hormones, nucleic acids of the host plant which

causes gall formation.

6. Enzymes or enzyme like secretions in the saliva are responsible for gall induction.

7. Salivary secretions of the insect serve as precursors to growth promoters or salivary

proteolytic enzymes convert plant protein into amino acids by hydrolysis.These abnormal

amino acids like nopaline, octopine etc. lead to abnormal growth.

8. Insect produces specific cecidotoxin which is responsible for gall formation.

9. Presence of Tumor inducing plasmid or tumour inducing principle in the salivary

secretions causes abnormal growth.

10. The tumour has the capacity to synthesize auxin or salivary secretion contain substances

that prevent degradation of auxin. High concentration of auxins in the gall tissue leads to

hypertrophy and hyperplasia and gall formation.

11. Amino acids present in the salivary secretions of gall-inducing insects, essentially lysine,

histidine, and tryptophan, could function as “preconditioners” for gall induction. It seems

that these amino acids could cause major plasticity and would increase the sensitivity of

the plant tissue to the action of the corresponding inducing insect.

12. It has been speculated that polyphenol oxidase (PPO), also present in the saliva

secretions of insects and the phenolic compounds derived from its enzymatic action,

could increase plant tissue sensitivity to the stimulus of the inductor insect. It has also

been suggested that the complex interaction between the host plant tissue and polyphenol

oxidase might be of fundamental value in gall formation. Interactions and the balance

between insect polyphenol oxidase and the host plant could determine whether the

“attack” of an insect causes injury (necrosis) or gall development.

13. The modulation of redox potential has been related to gall initiation and

establishment, especially concerning the accumulation of reactive oxygen species .

14. Different studies have reported that indoleacetic acid (IAA) could be a powerful

gall- inducing agent, and it has also been speculated that this compound could interact

with other plant growth regulators, like cytokinins and gibberellins, or in a synergistic

way with other chemical substances, to promote the induction and maturation of these

structures.

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15. Symbiotic relationships between gall-inducing insects and microorganisms have

been hypothesized to be involved in plant gall development. Some researchers have

reported that simultaneous infection with different species of endosymbionts in the same

host organism is a common phenomenon in several insect groups.

16. Secretions of phytohormones, such as cytokinins, by endosymbiotic

microorganisms have also been associated with the plant–galling insect interaction. The

inducing insects obtained their ability to induce galls via endosymbiotic microbes, which

have acquired the biosynthetic pathways to produce IAA and trans-zeatin family

cytokinins from plants.

17. It has been proposed that galling insects acquired genes from symbiotic

microorganisms through horizontal gene transfer . Horizontal gene transfer (HGT) is the

movement and transference of genetic information between different organisms, and it is

a common phenomenon between pathogens of animals and plants, and between

symbionts and pathogens. The mechanism through which Agrobacterium

tumefaciens transfers genes from the bacterium to plant cells occurs through the action of

the T-DNA segment present in the Ti plasmid.

MSc 3rd Semester

Material: "virus symptom"

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Material: "Introduction to plant galls"

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Material: "introduction and history of Plant pathology"

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