Physico-chemical attributes of seed oil from drought stressed sunflower (Helianthus annuus L.) plants

The effects of water deficit conditions on the qualitative and quantitative characteristics of sunflower seed and seed oils were assessed. Two sunflower cultivars (Gulshan-98 and Suncross) were sown in the field. The water stress treatment was applied at the vegetative or the reproductive stage. Analysis of the sunflower seed showed that the oil content decreased (a decline of 10.52% relative to the control) significantly (p <= 0.05) due to water stress when imposed at either of the growth stages. Both of the sunflower cultivars studied showed differential responses to water stress with respect to oil oleic and linoleic acid contents. A significant negative correlation in oil oleic and linoleic acid was observed in cv. Gulshan-98 under water deficit conditions as compared to Suncross in which no such effect of water stress on oleic and linoleic acid was observed. Water deficit conditions caused a reduction in linolenic acid in Gulshan-98, whereas it remained unaffected in Suncross. The stearic acid content increased in cv. Gulshan-98 due to drought, whereas no effect due to water stress was observed on oil palmitic acid content in either sunflower cultivar. Overall, oil unsaturated fatty acids remained unchanged in the drought stressed or normally irrigated plants of both cultivars but saturated fatty acid increased in Gulshan-98. Individual (alpha, gamma, and delta) and total tocopherol contents in the seed oil increased significantly with the application of water stress in both cultivars. An assessment of the physical and chemical characteristics of the oils of both sunflower cultivars revealed that drought stress caused a marked increase in the content of un-saponifiable matter (18.75% with respect to the control) and a decrease in iodine value (5.87% with respect to the control), but saponifcation value, density, specific gravity and refractive index remained unchanged.