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Changes in the composition of fatty acids (FA) were determined in lipid extracts isolated from developing ovaries containing ovules and developing seeds of Echium vulgare L. The samples were collected successively over 20 days beginning with the first day after flowering. The contents of the n-6 FA family members, i.e., gamma-linolenic (GLA) (C(18:3)) and linoleic (LA) (C(18:2)) acids changed in a parallel manner and reached the maximum of 13.9% and 24%, respectively, on the 12th day, after which they fell systematically down to 8.6% and 18.2%, respectively, on the 20th day after flowering. Starting with day 13, the content of alpha-linolenic acid (ALA) (C(18:3) n-3) begins to grow intensively, from 24.2% to 39.3% on the 20th day after flowering. The increase in the content of stearidonic acid (SDA) (C(18:4) n-3), up to 10.5% on the 20th day after flowering, occurred steadily as the seeds developed, and was independent of the changes in the content of GLA and LA. The pattern of changes in the content of SDA, GLA, LA and ALA during the development of seeds, and the occurrence of SDA in the seed oil of other plants, demonstrate that the biosynthesis of SDA in the seeds is critically dependent on the presence of ALA. The above condition indicates that SDA biosynthesis in the seeds of Echium vulgare follows the scheme LA --> simultaneous, competitive, action of Delta(6) and Delta(15) desaturases, leading to the formation of GLA and ALA, respectively, and then ALA (Delta(6) des) --> SDA. The biosynthesis according to the scheme: GLA (Delta(15) des) --> SDA is highly unlikely.

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The acute oral MLD of parathion to ewe and ram lambs of 20 kg body weight was approximately 40-50 mg a.i.jkg body weight. The insecticide was not markedly cumulative in its toxic effects.Pastures were topdressed with granules of 20% parathion at the rates of 3.4 kg and 6.7 kg a.i.zha and groups of four sheep were grazed on the pastures after withholding periods of 0, 7, 14, and 28 days. Sheep in the O-day groups developed slight scouring and their blood cholinesterase activity was severely depressed. None of these sheep died and their subsequent recovery was uneventful. In the other groups the only evidence of exposure to parathion was depression of blood cholinesterase activity, which was progressively less as the length of the withholding period increased. No parathion was detectable in the fat of the sheep that had the highest exposure to parathion on the treated pastures.Over a 3-month period parathion residues in topsoil (0-2.5 em) decreased from 6.5 ppm to 4.7 ppm and from 10.7 ppm to 8.5 ppm for application rates of 3.4 kg and 6.7 kg parathion/ha, There was little penetration of insecticide below the top 2.5 em of soil, and no parathion was found in the soil 8 months after treatment.Residues of parathion on pasture were more persistent in this grazing trial than in a subsequent ungrazcd plot trial. Parathion was not systemic in pasture, as residues were present apparently only on the plant surfaces.