Abstract: Taking the field cultivated oil peony 'Fengdan' as the research object, samples of peony follicles were collected every 10 days from flowering to maturity. The 100-grain weight, water content, oil content, and fatty acid content of the seeds were measured. The Richards equation for the days after flowering and the 100 grain dry weight was established to simulate and validate seed filling, which was used to analyze the filling characteristics of oil peonies. The dynamic changes of seed fatty acids and their components had been studied. The results showed that:（1）The filling speed of oil-used peony increased at first, reached the maximum at 52.10 days after flowering, and then decreased continuously. The dry matter accumulation process of oilseed conforms to the "S" growth trend of "slow-fast-slow", which can be expressed by Richards equation W=39.5874/（1+12729.09e^-0.1654t）^1/2.30312（R²=0.9787）. Among them, 42.24 to 61.96 days after flowering was the rapid increasing stage which occupied only 17.89% of the filling stage, but the contribution rate of grain filling was 33.10%. (2) The change trend of oilseed oil content with the process of grain filling was similar to that of dry matter accumulation. Oilseed oil content increased rapidly from 40 to 90 days after flowering. This period accounted for only 45.45% of the whole grain filling period, however, 82.11% of the oil accumulation in the whole grain filling period was completed. (3) In the process of oilseed filling, there was a significant negative correlation between grain water content and oil content, and a significant positive correlation between 100 grain weight and oil content. (4) The contents of each fatty acid in peony oilseed increased with the progress of grain filling, and the five main fatty acids content showed a trend of linolenic acid > linoleic acid > oleic acid > palmitic acid > stearic acid. Except for linolenic acid, the mass fraction of unsaturated fatty acids to total fatty acids increased during the whole grain filling process. Oleic acid increased slightly, linoleic acid had a small increase in the early stage, but remained stable in the later stage. The mass fraction of saturated fatty acids to total fatty acids increased at first, remained relatively stable from day 50 to day 90, and then decreased continuously. In order to prevent the reduction of material accumulation and shortening of grain filling period caused by premature aging of plants, further optimization of water, fertilizer and other control measures which was used to improve the matching degree between oil-used peony and field microclimate is the key to high yield and quality cultivation of oil-used peony in this area.

Key words: Oil peony, Grain filling, Richards model, Fatty acid, Dynamic change