Carolyn S. James

The enantiomeric composition of triadimenol produced during metabolism of triadimefon by fungi: III. Relationship with sensitivity to triadimefon

Abstract Fifteen species of fungi, grown in shake culture in a liquid nutrient medium containing a 50:50 mixture of the 1 R and 1 S enantiomers of triadimefon, reduced triadimefon to triadimenol, the extent of reduction varying from 95% according to species. Each produced its own characteristic pattern of two or more of the four possible enantiomers of triadimenol and the stereoselectivity and stereospecificity of the reduction is discussed. The sensitivity of each fungus to individual enantiomers and a mixture of enantiomers of triadimefon and of triadimenol was assessed. Three broadly defined groups of fungi were found: (i) sensitive to both triadimefon and tridimenol, (ii) insensitive to both, and (iii) insensitive to triadimefon but moderately sensitive to triadimenol. In many cases it was possible to predict, at least semiquantitatively, the sensitivity of an organism to triadimefon from a knowledge of its characteristic metabolism to triadimenol and its sensitivity to the individual triadimenol enantiomers. No evidence for synergism or antagonism was found.

Fluidity and lipid composition of oat and rye shoot plasma membrane: effect of sterol perturbation by xenobiotics

Oat and rye plants were treated with either tetcyclacis (an experimental plant growth regulator), nuarimol (a fungicide) or gamma-ketotriazole (an experimental herbicide). These treatments reduced shoot growth and changed the lipid composition of the shoot plasma membranes. In oat, both tetcyclacis and nuarimol treatments increased plasma membrane cholesterol and increased the phosphatidylethanolamine/phosphatidylcholine (PE/PC) ratio, whereas gamma-ketotriazole treatment reduced cholesterol and the PE/PC ratio. In rye, all treatments reduced the PE/PC ratio. Generally, the sterol/phospholipid ratio was less in oat than in rye but the cholesterol/phospholipid ratio was greater. With all treatments in oat and rye, increases were observed in unsaturation of the phospholipid acyl chains. The fluidity of membranes was measured by steady-state fluorescence polarisation of the probe diphenylhexatriene; oat membranes were more fluid than rye. Membrane fluidity was greater in plasma membranes from plants treated with the xenobiotics than the controls. The results are discussed in the context of the effect of plasma membrane lipid composition on membrane fluidity, and it is concluded that there appears to be no overall simple relationship between membrane lipid composition and fluidity that holds for all treatments in both species.

Characterization and lipid composition of the plasma membrane in grape leaves

Abstract Plasma membranes have been isolated from grape leaves using a two-phase aqueous polymer technique which differed from the usual procedure in order to counter difficulties posed by the fibrous nature and high starch content of this material. The lipid composition (sterols, phospholipids + sphingolipids and their fatty acids) of the purified plasma membrane was determined and compared with that of the microsomal fraction (100 000 g). The major differences between the membrane and microsomal fractions were increases in the proportions of stearic acid, phosphatidylcholine and, to a lesser extent, phosphatidylethanolamine and a decrease in linolenic acid. Phosphatidylglycerol and diphosphatidylglycerol were present in the microsomal fraction, but not in the plasma membrane. Unusually large amounts of cerebrosides (compared with some other plant species) were found in both membrane fractions. The lipid composition of the plasma membrane is discussed in the context of membrane fluidity.

Photolysis of diclobutrazol in methanol

Abstract The fungicide diclobutrazol (2RS,3RS)-1-(2,4-dichlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-ol was irradiated by ultra-violet light in methanol solution using (1) borosilicate glass apparatus and (2) quartz apparatus. The major differences observed were that photodegradation occurred more rapidly in (2) than (1) and more breakdown products were found in the former. Using g.c.-m.s. ten compounds were detected in (1) of which five were identified. In (2) twelve of the eighteen compounds observed were identified and the major component was 1-(4-chlorophenyl)-4,4-dimethyl-2-(1H-1,2,4-triazol-1-yl)pentan-3-one. The compounds reported were formed by oxidation, loss of chlorine or by cyclisation. This previously unreported cyclisation gave the s-triazolo-(5,1a)isoquinoline ring system.