Graduate Thesis Or Dissertation
 

The effect of harvest date and pre-storage drying methods on capsule thebaine yield, seed oil yield, and seed germination of two accessions of Papaver bracteatum Lindl.

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  • A field study was conducted in 1978 and 1979 at the Hyslop Crop Science Field Laboratory near Corvallis, Oregon, to determine the optimum capsule harvest date of Papaver bracteatum Lind. for thebaine yield and oil yield, while maintaining an acceptable percentage of seed germination. Accessions PI 383309 and PI 381607 were chosen for this study because of their superior yield characteristics. The effects of pre-storage drying of harvested plant materials on the yields and seed germination were studied in the second year of the experiment. Both accessions responded similarly to all treatments. The effects of harvest dates on the yield components and seed germination were comparable in the two years of the study except for the seed yield. The difference for the seed yield was due to earlier capsule maturity in 1979 that resulted in earlier seed shattering in that year. Drying of the harvested plant materials in a dryer immediately after harvest did not significantly affect the oil and thebaine yields or the percentage of seed germination. Although the data for the thebaine concentration of the capsules in 1978 were of questionable accuracy, capsule thebaine yield was not significantly different for the harvest dates later than four weeks after petal opening. Seed oil yield was not significantly affected by the harvest dates in 1978. However, in 1979, seed oil yield for the harvests later than seven weeks after petal opening were significantly lower than that on the earlier harvest dates. While seed oil content was very stable, seed shattering was responsible for the decline of seed oil yield on the later harvest dates in both years of the study. Seed shattering was more pronounced in the second year of the study when plants produced larger capsules and more seeds. Seed germination was not significantly affected by the harvest dates. Seeds were found to be viable four weeks after petal opening, or earlier, although they continued to develop in the capsules for two to three weeks after that date. Seven weeks after petal opening was found to be the optimum capsule harvest date under the climatic conditions of the experimental site. Thebaine yield of approximately eight kilograms per hectare was calculated for the capsules harvested on that date. Forty-five kilograms of oil were obtained fromthe seeds of capsules harvested seven weeks after petal opening in 1978. This yield was significantly higher in 1979 when it exceeded sixty-five kilograms of oil per hectare. Generally, total seed oil yield and capsule weight of both accessions increased, while capsule thebaine concentration tended to decrease as plants increased from two to three years of age.
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