Study On Formation Mechanism Of Oil Quality In Tree Peony Seed

Tree peony Cultivated species ’Fengdanbai’ of 8 years old was selected as the study samples. The development characteristics of tree peony pods and seeds were observed, the transformations of the main nutrients were analyzed, the fatty acid constituents and relevant enzymes and tree peony seed metabonomics were measured. Expect to provide the scientific basis for the exploitation of tree peony seed oil. The results were as follows:(1) The four marked stages in the development of tree peony seeds were observed at the early fertilization and grain formation stage(S1), the rapid growth stage of pod and seed(S2), the seed inclusion enrichment and conversion stage(S3), and the late dehydration and maturity stage of pod and seed(S4). Among them, S1 is the key period of tree peony seed number formation, while S2 and S3 determine the storage capacity of tree peony pod, S4 determines the final seed yield and tree peony oil quality. The volume and weight of tree peony pods and seeds reached the highest and inclusion transformation basically completed, while pod skin dehydration and change from green to yellow and seeds change from yellow to back when tree peony pods into the dehydration stage. Tree peony pods began cracking and seeds dropping and the content of crude fat decreased slightly after flowering 110 ~ 115 day. The pods cracking and seeds dropping were easy to cause unnecessary economic loss and recovery difficult. Therefore, suggestions harvest tree peony seeds before pods cracking in order to achieve high yield and high quality objective.(2) Tree peony seeds belong to oil seed. Sugar, protein and fat are the main nutrients. Seed moisture content decreased with organic matter increased during seed maturation. Before the late dehydration and maturity stage of pod and seed(S4), seed moisture content was negatively correlated with crude fat accumulation(R =- 0.884**). Seed moisture content was higher before the seed inclusion enrichment and conversion stage(S3). Tree peony pods moisture content were decreased and stabilized with the accumulation of seed starch, protein and other major nutrients; while the organic metabolic of tree peony pods have turned the synthesis and transformation of triglycerides and other substances. The soluble sugar content was negatively correlated with crude fat accumulation(R =- 0.935*), described the soluble sugar transformed into a large number of triglyceride and the rapid increase in the accumulation of crude fat. Leaves chlorophyll content increased significantly and was significant positively correlated with pods skin soluble sugar, seed soluble sugar and free amino acids(R = 0.748**, 0.705**, 0.816**). The accumulation of tree peony pods skin chlorophyll was rapidly before the crude fat, indicating pods skin can also carry out photosynthesis and photosynthetic products transported mainly into seeds in the form of sugar.(3) Seeds major fatty acids are unsaturated fatty acids which content was 92.28%. The relative contents of oleic acid and linoleic acid were upward. Both the oleicacid and linoleic acid were significant negatively correlated with linolenic acid contents(R =-0.865**,- 0.916**), and negatively correlated with Palmitic acid(R =- 0.917*,-0.675*). Saturated fatty acid is mainly palmitic acid and stearic acid. The content of palmitic acid declined slightly and was significant negatively correlated with the content of unsaturated fatty acids(R =- 0.974**), which showed the tree peony seeds transforming between fatty acid components have a complex internal relations. Meanwhile, the dynamic changes of isocitrate dehydrogenase(IDH), isocitrate lyase(ICL), glucose-6-phosphate dehydrogenase(G6PDH), pyrophosphatase(PPase) and pyruvate dehydrogenase(PDH) activity were consistent with crude fat content. The activity of G6 PDH was positively correlated with the content of protein and starch in seeds(R = 0.536*, 0.570*). The activity of PPase was significant negatively correlated with the content of protein in seeds(R =- 0.725**). The activity of isocitrate lyase was positively correlated with the content of soluble sugar and free amino acids in seeds(R = 0.659*, 0.577*).(4) Tree peony seeds of Metabolomics 195 kinds of compounds were detected. As was mentioned for the data heat map above, the seed data showed many carbon pathway compounds tended to drop through development, such as Sucrose, fructose-6-phosphate, UDP-glucose are at higher levels early in development, then decline as galactinol is sharply increased in Stage 3. Most free amino acids declined over time, especially in the last phase of development the amino acids declined precipitously, the assumption being that they are incorporated into seed proteins. It is interesting that the aromatic amino acids(alanine, tryptophan and tyrosine) in seeds followed an unusual pattern, being highest in Stage 3, but then declining in Stage 4. The 1-stear oylglycerol accumulation in the early development, this process is mainly carried forward plastid. The oleate was accumulated rapidly at the seed inclusion enrichment and conversion stage, and slightly reducing at the late dehydration and maturity stage of pod and seed. Although 1-linoleoylgylcerol and 2- linoleoylgylcerol were more significant at the seed formation stage, but at a lower level than other three periods. The linolenate firstly increased and then lower, but the overall level was significantly higher than other unsaturated fatty acids. For instance, gamma-tocopherol and delta-tocopherol, as well as ascorbate and glutathione underwent dramatic increases at the either rapid growth stage of pod and seed(S2) or seed inclusion enrichment and conversion stage(S3). Meanwhile, both the oxidized and reduced forms of glutathione accumulated in the late stages of development, along with strong increases in gamma-glutamyl amino acids. The gamma-glutamyl amino acids increased is mainly for amino acid of seed germination required preparation. Secondary metabolites in seeds(e.g. quercetin-3-Oglucoside, luteolin-7-O-glucoside and kaempferol-3-O-beta-glucoside) tended to decline with seed development.