bioassay test of herbicides

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WELCOME

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PRESENTATION ON

“BIOASSAY TEST FOR HERBICIDES”

Course title: Principles and practices of weed management,Agron-503

Course lecturer and ppt. Assigner: Dr.T.U.Patel Asst.Proff.

Dept.of Agronomy,NMCA,NAU.

Presenter :

Mahesh.B.Tengli Jr.M.Sc (Agri) Extn.Edu.

Semester: I,NMCA,NAU.

2014-2015

M.B.Tengli M.Sc(Agri) Extn.Edu.,NMCA,NAU

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OUTLINE

† Introduction† Defining bioassay† Indicator species† Assessment parameters† Application of bioassay † Bioassay procedure † Bioassay techniques/ tests † Advantage and disadvantage of bioassay technique† Reference


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INRODUCTION

“B I O -A S S A Y”

Wattt is ASSAY?


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Assay –means ---EXAMINATION ,ANALYSIS,DETERMINATION

Defining assay : Assay refers to analysis ,examine or determine the presence ,absence or quantity of one or

more components.


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Y 2 ASSAY ?


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• In the context to herbicide residues in plants and soil they pose serious threat to -----subsequent sensitive crops, soil microbes, and human and animal health.


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•In order to know effects of such act of herbicides, we need to assay i.e. analyze, examine, determine the presence herbicides in soil.

8M.B.Tengli M.Sc(Agri) Extn.Edu.,NMCA,NAU

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ASSAY

ANALYTICAL

TECHNIQUE

BIOASSAYTECHNIQUE

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BIOASSAY

•Etymologically ,bioassay can be studied by splitting it into two words i.e. bio-assay.•Bio- life •Assay – examining, determining, analyzing.•Combining above both words we can define “bioassay” .


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Defining “Bioassay”

Process of determining the relative strength of a substance viz. herbicides by comparing its effect on a test organism /indicator species with that of certain standard preparation.


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Indicator species, watttt is it ?

It is any biological species such as plants, microbes ect. Which is highly sensitive to the minute changes in its environment & within having a capability of signifying the effect of any disturbance , might be due to presence or absence of a toxin(herbicide), and organism etc..


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Characteristics of indicator species

•May be microbes (lichens) or plants (sorghum).•Highly sensitive to minute changes in chemical.•Effects should be easily and clearly observable

and measurable.


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Indicator ssp. commonly used in herbicide assay-

•Cucumber•Sorghum•Mustard•Soybean•Oat•Minor millets


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•WENN… Bioassays should be conducted ?

• when newly seeded or established plants exhibit abnormal growth injury.• when seeding or planting on areas previously treated with herbicides known to be residual.• when using abandoned farmland, which may contain herbicide residues.• when using non-cropland, such as railways, roadsides, storage areas, and industrial sites that may contain herbicide residues.• when purchasing livestock manure or topsoil of unknown origin.


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Assessment parameters

The response of indicator plants to herbicides can be evaluated in various ways as follows…•Germination test•Assessment of plants •Physiological and Morphological effects•Symptoms


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Germination test

• The herbicides has the ability to inhibit germination of sensitive plants ,effect is seen based on counting number of seedlings germinated.•Sub lethal concentration of herbicides inhibit shoot elongation this is related to dosage which can be measured.•Indicator species used are :

cucumber ,sorghum and oat M.B.Tengli M.Sc(Agri) Extn.Edu.,NMCA,NAU

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Assessment of plants

•Determination of dry weight is the most common assessment used in bioassay.•By estimating the dry weight and fresh weight of sensitive plant herbicide residue is estimated.•Dry and fresh weight are taken from the top portion i.e. shoot since uprooting the plant along root is laborious work.


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Continued…

•In case of photosynthesis inhibiting herbicides , shoot growth is reduced before the appearance of the injury symptoms .•By measuring the plant height or leaf length provides an assessment of herbicidal activiety.


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Physiological and morphological effects:

•Here the physiological, bio-chemical and structural modifications of plants induced by herbicides are used for bioassay assessment.•Cholrosis can be evaluated by determining chlorophyll content through spectrophotometer.•Decrease in viability of root tissue is determined by modified teterazolium test.


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Symptoms

•Certain group of herbicides produced a typical symptoms in plants this can be used for qualitative assay ,if the symptoms are related to dosage then such symptoms can be used for quantitative assay.•Example : Epinasty of cotton due to 2,4-D.


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Application of bioassay.

•In studying the effect of soil factors on

herbicidal activity.•In studying dissipation from soil surface.•In studying movement of herbicides in soil.•In studying degradation and persistence of

herbicides.

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Bioassay procedure.•Generally the procedure developed by "Crafts”(1935)•Indicator plants are sown in the soils which are

treated with herbicide at different concentration.•Measurements such as germination, plant height and

dry weight of indicator plant and standard curves are

drawn , these readings are compared with

predetermined standards or parameters obtained from

field sample.


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Bioassay techniques:

•Field assay•Laboratory •Greenhouse assay•Foliar assay


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Field assay:

•The field plot is treated with herbicide •In the same plot indicator plant is grown at

various time intervals.•Growth of test plant is used as a measure for the

presence or absence of the herbicide.•Cucumber, Sorghum, Mustard, Soybean, Oat and

Minor millets.


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Laboratory assay:

•Experiments are conducted in laboratory using

different substrates(soil and agar under

controlled conditions).•Solution assay are conducted in containers like

petridish,basket,flasks or test tubes.•For soil assay plastic petridishes, wax papers or

earthen pots are used.•In agar solidified agar is used in petridish.


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Greenhouse assay:

•Here experiments are conducted in big pots or

plastic containers and kept in greenhouse to

study the dissipation and leaching behaviour of

herbicides from different types of soils.


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Foliar assay:

•Here herbicide are applied directly to the foliage

of test plant.•This technique is adopted mainly to study

residues in plants.


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Advantages of bioassay:

•Economical.•Easy to perform.•No need to extract substrate from test sample.•It assures that the phytotoxicity activity of

herbicide molecule is being measured.


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Disadvantage of bioassay:

Exact quantity of herbicide residue cannot be measured.

Indicator plant may some time be effect by other factors and give undesirable results.


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Reference

•Study material from Dr.T.U.Patel Asst.Proff.

Dept.of. Agronomy•Laboratory manual of weed sciences by Dept.of

Agronomy ,UAS Raichur, Karnataka.


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31Thank you

“Nature is God’s Art”

“Maintaining Beauty of Nature is Nature’s Art”

“Human Life is Nature’s Art, Maintaining the Beauty of Life is Man’s Art”

“Art is Mother of Science”

“Agronomy is Art and Science that is why ,

Agronomy is Mother of Agriculture Science”

Written by Mahesh.B.Tengli


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bioassay test of herbicides

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