Plant Growth Regulating Properties of Sulphonamides and Some Aspects of Phenoxyacetate Herbicide Photochemistry

Organic chemistry, Agriculture

Phillips, Michael J

University:University of Glasgow

关键词: Organic chemistry, Agriculture;   

Others  :  http://theses.gla.ac.uk/78043/1/11007322.pdf

来源: University of Glasgow

【 摘 要 】

The work contained in this thesis is primarily an investigation of the biological and chemical properties of a variety of herbicides and related compounds. Two classes of compounds were studied. One included asulam and structurally related sulphonamides. The other was the phenoxyacetate salts and esters. The work can be summarised as follows: Chapter 2: All of the test sulphonamides were found to reduce the fresh weight of test plant seedlings. Growth inhibition of cress seedlings was overcome by adding p-aminobenzoic acid. Results indicated the competitive inhibition of the enzyme dihyropteroate synthetase. Field experiments involving bracken were inconclusive. Chapter 3: Test sulphonamides containing aliphatic and five- membered heterocyclic groups were more effectively able to penetrate bean leaves than those containing six membered heterocyclic groups. Low humidity reduced foliar uptake in all cases. Tween 20 was found to improve penetration in most cases. Tween 80 and ammonium thiocyanate (NH4SCN) had no effect on penetration. Chapter 4: Asulam and three test sulphonamides were rapidly degraded in both soil types used, particularly over the first few days of the experiments. Asulam was less readily degraded in an aged soil sample (3 months). There was some chromatographic evidence for the generation of sulphanilamide as a metabolite. Chapter 5: Literature review. Chapter 6: Irradiation of 4-chlorophenoxyacetate (CPA) and 2-methyl-4-chlorophenoxyacetate (MCPA) with light from a medium pressure mercury arc lamp in the presence of NH4SCN generated the thiocyanate and isothiocyanate derivaties respectively. Two isomeric phenyl acetic acid photoproducts were generated from the irradiation of sodium phenoxyacetate (PPA). Chapter 7: Using the butyl esters of PAA, 2,4-D and MCPA, vitamin C was the most effective photostabiliser in the presence of UV light. Vitamin E, phenothiazine, p-nitrophenol and 8-hydroxyquinoline showed useful activity but only at higher concentrations. Potassium iodide (KI) and NH4SCN were least effective.