| Soybean isoflavones were important secondary metabolites in soybean plants, which have many biological functions such as weak estrogenic activity, promoting nodulation and limiting the exogenous microbial growth. Four soybean varieties which had significant diference in isoflavones were chosen as main study objects in this research. This research compared the difference of accumulation of soybean isoflavones between SC and RC, systematically studied with dynamic change of PAL activity as well as the relationship between soybean isoflavones in leaves and seeds and field microclimate. Test also studied dynamic changes of soybean isoflavones content in seeds under SC and RC conditions during after-ripening periods. The main results were described as follows:1. Using ethanol extraction, two key factors (solid-to-liquid ratio and extraction time) were explored by completely randomized experiment. The results showed that solid-to-liquid ratio was significantly affected extraction rate of isoflavones, the optimal extraction conditions were:solid-to-liquid ratio 1:40, ultrasonic extraction 30min. Three key factors (hydrolysis temperature, pH and hydrolysis time) were explored by L9(34) orthogonal test. The results showed that 65℃, pH13,40 min was optimal hydrolysis conditions, the hydrolysis rate was 100%, and there was no G-type isoflavones hydrolyzed into aglycones.2. Variation trends of PAL activity in SC and RC soybean leaves were all showed "slowly increasing-rapidly increasing-rapidly declining", the average rates of which were 1:3/d,8.2/d and-11.2/d respectively. The lengths of slowly increasing period were different among varieties with different growth period. Compared PAL activity of SC soybean leaf with RC soybean leaf, results showed that PAL activity of RC soybean leaf was lower during slowly increasing period, the increase rate was higher during rapidly increasing period and the decline rate was lower during rapidly declining period respectively.Thus, RC didn't have bad effect on the rapidly increasing process of PAL activity.3. Variation of isoflavone content in leaves and seeds of SC and RC soybean during development phase were compared. Isoflavone content in leaves showed "slow rise-to keep-sharp decline". In SC and RC soybean leaves the average content were 0.364 and 0.345 mg.g-1 during content retentionint, and dropped 0.251 and 0.208 mg.g-1 during sharp decline phase respectively. Accumulation of M-type, G-type and total isoflavones were all divided into initial accumulation and fast accumulation period, the division method of G-type was the same as total isoflavones.37 days after flowering of Nandou 5 and 44 days after flowering of rest varieties to harvest time were fast accumulation period for SC soybeans. The fast accumulation period of RC seeds was 7 days later than that of SC seeds except Nandou 5. The average accumulation rate of fast accumulation period of SC and RC seeds were 0.0555 and 0.0570 mg·(g·d)-1, and isoflavone accumulation of which were 73.83% and 63.50% of total accumulation respectively. In addition, the difference of accumulation trend between two planting patterns of G-type was greater than M-type. Thus, isoflavone accumulation was affected by planting patterns. The differences of sensitivity for RC existed in components or varieties.4. Dynamic changes of isoflavone content in soybean seeds during after-riping process were studied. The results showed that G-type, M-type and total isoflavone content were all showed increased firstly and then decreased, the difference of time that isoflaxone content reached the highest value exsit in planting patterns or varieties. During after-riping process, maximum accumulation of total isoflavone were 9%-36% and 14%-39% of total accumulation of SC and RC seeds respectively, and M-type increment was higher than that of G-type. The total isoflavone maximum accumulation of Weiyuan and Nandou 5 in SC seeds were significantly higher than that of RC. Multiple comparisons of average total isoflavone content at different times showed that air dry for 7 days of SC seeds and 14 days of RC seeds could get highest content seeds. Thus, proper air dry process was conducive to isoflavones accumulation in soybean seeds, and RC seeds needed longer air dry time.5. The temperature and PAR of RC growth zone were significantly or highly significantly lower than that of SC growth zone, and RH showed the opposite rule during Maize/soybean symbiotic period. Three factors'direct effect on the total isoflavone content showed PAR>temperatur>RH through Path analysis, and remaining path coefficients for seed was greater than leaf. Correlation analysis showed that the total isoflavone content in leaves and seeds were significantly positive correlated with temperature and PAR, and significantly negative correlated with RH.6. Correlation analysis between the highest isoflavone content in SC or RC seeds and agronomic traits as well as quality traits were compared. The results showed that difference of correlation between G-type, M-type, the highest total isoflavone content and agronomic traits exist in Sc and RC seeds, of which the difference of correlation between content and height was most obvious, that was significant positive correlation under SC and negative correlation under RC. For SC and RC seeds, isoflavone content were all negative correlated with protein content, and all positive correlated with fat content.
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