Glyphosate use in agro-ecosystems [Elektronische Ressource] : identification of key factors for a better risk assessment / presented by Tsehaye Tesfamariam Habtemichael

Tesfamariam

Informations

• Publié par: universitat_hohenheim
• Publié le: 01 janvier 2009
• Nombre de lectures: 30
• Langue: English
• Poids de l'ouvrage: 4 Mo

Extrait

Institute of Plant Nutrition (330B)
University of Hohenheim
Prof. Dr. V. Römheld





GLYPHOSATE USE IN AGRO-ECOSYSTEMS: Identification of key
factors for a better risk assessment.




Dissertation
Submitted in fulfillment of the requirements for the degree “Doktor der
Agrarwissenschaften” (Dr.sc.agr./Ph.D. in Agricultural Science)

to the

Faculty of Agricultural Science







Presented by
Tsehaye Tesfamariam Habtemichael
Born in Berakh, Eritrea

2009














This thesis was accepted as a doctoral dissertation in fulfillment of the
requirements for the degree "Doktor der Agrarwissenschaften" (Dr. sc.
agr. / Ph.D in Agricultural Science) by the Faculty of Agricultural
Sciences of the University of Hohenheim on 02.09.2009.





Date of oral examination: October 7, 2009.





Examination Committee:

1. Supervisor and Review Prof. Dr. V. Römheld
2. Co-Reviewer Prof. Dr. R. Gerhards
3. Co-Reviewer Prof. Dr. W. Claupein
Vice-Dean and Head of the Committee Prof. Dr. W. Bessei

Table of contents 


Chapter 1 .......................................................................................................................... 1
1.0 General introduction.................................................................................................... 1
1.2. Glyphosate discovery and development .................................................................... 1
1.3. Biochemistry of glyphosate ........................................................................................ 2
1.4. Herbicidal mode of action .......................................................................................... 3
1.4.1. The shikimic acid pathway ...................................................................................... 5
1.5. Glyphosate metabolism in plants ............................................................................... 6
1.6. Dissipation mechanisms in soil .................................................................................. 7
1.7. Interaction of glyphosate with other soil minerals ...................................................... 9
1.8. Implications of glyphosate discovery ....................................................................... 10
1.8.1. Strategy for obtaining glyphosate resistant crops ................................................ 11
1.9. Glyphosate intoxication of non-target organisms .................................................... 12
1.9.1. Routes of drift contamination to non-target organism .......................................... 13
1.9.2. Rhizosphere transfer of glyphosate from target to non-target organisms ............ 13
1.9.3. Glyphosate toxicity on soil microbial community .................................................. 15
1.9.4. Interaction between glyphosate and fungal disease ............................................ 16
1.10. Objectives: ............................................................................................................. 18

Chapter 2 ........................................................................................................................ 20
2.0. General Materials and Methods............................................................................... 20
2.1. Plants material ......................................................................................................... 20
2.2. Used soil .................................................................................................................. 20
2.3. Conditions for plant growth ...................................................................................... 21
2.4. Glyphosate application ............................................................................................ 22
2.4.1. Rye grass pre-culture and glyphosate application............................. .. ........ .......22
2.4.2. Glyphosate soil application................................................................................. . 23
2.5. Sunflower sowing ..................................................................................................... 23
2.6. “Waiting times” ......................................................................................................... 23
2.7. Plant harvest ............................................................................................................ 23
2.8. Shikimate analysis ................................................................................................... 23
2.9. Analysis of mineral nutrients .................................................................................... 24
2.10. Statistics ................................................................................................................. 24


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Table of contents 


Chapter 3 ........................................................................................................................ 25
3.0. Relevance of Waiting Time Between Weed Desiccation by Glyphosate and
Subsequent Crop Planting. ...................................................................................... 25
3.1 Introduction ............................................................................................................... 25
3.2 Materials and Methods ............................................................................................. 27
3.2.1. Greenhouse model experiment ............................................................................ 27
3.2.1.1. Conditions for plant growth ................................................................................ 27
3.2.1.2. Weed (rye grass) desiccation by glyphosate and cultivation of sunflower ........ 27
3.2.1.3. Plant harvest ...................................................................................................... 28
3.2.1.4. Shikimate analysis ............................................................................................. 28
3.2.2 Field Experiment .................................................................................................... 28
3.2.2.1. Conditions for plant growth ................................................................................ 28
3.2.2..2. Cover crop desiccation by glyphosate .............................................................. 29
3.2.2.3. Data collection ................................................................................................... 29
3.2..3. SPAD value measurement .................................................................................. 29
3.2.2.3. SPAD value measurement ................................................................................ 29
3.2.4. Analysis of mineral nutrients ................................................................................. 30
3.2.5 Statistics ................................................................................................................. 30
3.3 Results ...................................................................................................................... 30
3.3.1 Greenhouse model experiment ............................................................................. 30
3.3.1.1. Visual plant growth ............................................................................................ 30
3.3.1.2. Shoot and root biomass ..................................................................................... 31
.3.1.3. Intracellular shikimate accumulation .................................................................... 31
3.3.1.4. Micronutrient acquisition .................................................................................... 34
3.3.2 Field experiment .................................................................................................... 35
3.3.2.1. Visual plant growth ............................................................................................ 35
3.3.2.2. SPAD value and mineral nutrient acquisition .................................................... 38
3.4 Discussion ................................................................................................................. 40
3.4.1. Controlled greenhouse experiment ...................................................................... 40
3.4.2 Field Experiment .................................................................................................... 41
3.5 Conclusion ................................................................................................................ 43
3.6 Prospects .................................................................................................................. 43


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Table of contents 


Chapter 4 ........................................................................................................................ 44
4.0. Glyphosate transfer via the rhizosphere from target to non-target plants: Possibl