Effect of Foliar Application of Plant Extracts on the Growth Behavior and Quality of Evening Primrose (Oenothera biennis L.)

The indeterminate behavior of evening primrose is a frequent limitation in its cultivation. Controlling the final growth of plants at a certain stage is important. In the present ‎experiment, different plant extracts were compared functionally with ‎cycocel at different times of application. The experiment was performed as a factorial experiment based on a ‎randomized complete block design with three replications. Treatments included normal water ‎‎(control), cycocel (zero and 100 ppm), walnut (Juglans regia L.) leaf extract (zero and 25%), oak ‎fruit extract (Quercus castaneifolia L.) (zero and 25%), and cotton ‎capsule extract (Gossypium hirsutum L.) (zero and 25%). Evaluations were made on the seeds, oil yield and yield-components. The foliar application significantly reduced stem length (43-80%) and plant height (13-‎‎33%), but increased the percentage of oils (18.75%) and free fatty acids (67.5%). The highest ‎oil content (35%) occurred in response to a combination of walnut, oak, cotton extracts, and cycocel.‎‏ ‏The highest amount of free fatty acids (23%) indicated more immature‏ ‏seeds and ‎was obtained under the treatment of cotton extract. Natural extracts increased the oil percentage, but reduced ‎the free fatty acid percentage and the stem length. It seems that further studies in this ‎regard can help control non-terminal growth of evening primrose without having a need for breeding ‎programs.