Table II. Concentration of Ethalfluralin and Trifluralin Measured with a GC-MS-NCI and a GC-ECD0 j"vs concentration, rate, after ng/g of oven-dry soil kg/ha treatment GC-MS-NCI GC-ECD Ethalfluralin 1.0 199 46 50 1.5 199 124 129 1.0 555 12 12 1.5 555 16 23 standard error of mean for methods of analysis = 2.6 Trifluralin 1.0 199 122 126 1.5 199 206 192 1.0 555 57 65 1.5 555 89 85 standard error of mean for methods of analysis =4.80 Differences in concentration of trifluralin and ethalfluralin due to rates and sampling dates were significant and differences between GC-MS-NCI and GC-ECD were not significant (P = 0.05) by analysis of variance.(Lethbridge Research Station, unpublished data). Thus, the GC-MS-NCI can be used to confirm levels of ethalfluralin and trifluralin residues that are toxic to plants.The ability to analyze trifluralin and ethalfluralin with the GC-MS-NCI indicates that this system has potential for rapidly confirming structures and concentrations of several pesticides with a positive electron affinity in soil extracts. ACKNOWLEDGMENTWe thank Drs.

The bleaching effects of norflurazon [4-chloro-5-(methylamino)-2-(α,α,α-trifluoro-m-tolyl)-3 (2H)-pyridazinone] and of oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene] were compared using the intact microalgaScenedesmus acutusand the fungusPhycomyces blakesleeanus.Under the influence of oxyfluorfen, but not of norflurazon, pigments and membranes were degraded. This activity is typical for oxyfluorfen. Norflurazon prevented carotene synthesis, but did not cause degradation of carotenoids, chlorophylls, or35S-sulfolipid, a marker of photosynthetic membranes. Furthermore, light-induced ethane evolution byScenedesmusis substantial with oxyfluorfen, but not with norflurazon present. Oxyfluorfen apparently causes radical-initiated peroxidation of polyunsaturated fatty acids.

of changes in the activities of these enzymes may be known only after detailed analysis for free and protein amino acids, in vivo concentration of different metabolites, particularly in the vicinity of various enzymes, and chasing the fate of labeled NH4+, glutamine, and asparagine. On the basis of the resulte presented, it may, however, be suggested that in developing wheat grain, both the glutamate synthase cycle and the GDH pathway may be operative in ammonia assimilation, the former predominating during the early stages and the later playing a more active role during the later stages.