Effects of some Ggronomic Techniques on Oil Yield and Composition of Oenothera biennis L

Evening Primrose oil (Oenothera biennis L.) is a rich source of Gamma linolenic acid (GLA) and other useful unsaturated fatty acids. Despite the diversity of sources of GLA, due to better absorption in the human body, evening primrose oil is the main source of GLA. In this study, the effects of pollination, harvesting method and application of salicylic acid on yield, yield components, and quality of evening primrose oil were studied. A factorial experiment as a randomized complete block design with three treatments including pollination (pollination by bees, no pollinators and free pollinators), salicylic acid (0 and 200 ppm) and harvest method (normal harvest, pre harvest by flame) and four replications was performed. The effect of treatments on the oil yield, oil content, fatty acids composition and the content of free fatty acids of oil were studied. Results showed that the oil yield and oil percentage of plants which visited by bees were at the highest amount (1.87 gr/ plant and 33.6%, respectively). Compared to the control, the oil yield of plants which treated with salicylic acid significantly increased. Between two different harvest methods, the highest oil percent (31.6 %) was observed in plants treated with flame. Under the interaction effect of treatments, the highest oil yield (2.24 g/plant) was observed in combination of bee and salicylic acid 200 ppm and the highest free fatty acids (2.19%) accumulation was recorded in the open cage with 200 ppm salicylic acid. Since pollination increases the number of formed seeds per capsules, therefore, it is expected that simultaneous application of pollinator and pre-harvest treatment by flame increases seed yield, oil yield and quality which is partly shown in the obtained results of present study.