The influence of environment upon the composition of sunflower seed oils. II.—Composition of the seed oils of sunflowers grown in English gardens from five specimens of different African sunflower seed

Five specimens of sunflower seeds from Africa, the oils in which varied widely in composition (44–72% linoleic acid), were grown in three English gardens in West and East Cheshire and Kent. The composition of the resulting English‐grown seed oils was broadly the same in all cases, irrespective of the seed sown. Host of the oils contained, on an average, 68–70% of linoleic acid, but the extreme range of linoleic acid varied from about 60 to 75%. The apparent explanation of these subordinate differences may lie in the effect of direct sunlight on the ripening seed heads, Since flower‐heads that became completely inverted and faced downwards gave the oils with highest linoleic acid content; others, in which the stems turned more or less through 90° so that the heads were more freely exposed to direct light, gave oils with somewhat reduced linoleic acid content. It is concluded that varietal factors play little part in determining the composition of sunflower seed oils. The main effect is that high linoleic content is conditioned by slow development and ripening of the seed, and vice versa ; climatic (temperature) conditions and also, probably, the degree of incidence of light on the ripening seed heads are the factors which control the rate of development of the seed and also the relative unsaturation of the seed oil.