| Isoflavones of soybean (Glycine max(L.) Merri.)form a group of distinct secondary metabolites in soybean especial in seeds, which we paid much attention because of its biological functions. The research began with the scavenging of free radicals by flaviods, chose soybean isoflavones of four soybean varieties which had significant difference as main study object. This paper studied isoflavones distribution and change in the the whole growth period , then the accumulating rules have been inquired into. The research also probed in the relationship of metabolites between isoflavones and primary metabolites by studying the former materials of isoflavones synthesizing with the development of soybean seeds,and we studied the influence on antioxidant system by the accumulation of isoflavones. We also studied isoflavones its synthesizing key enzyme- phenylalanine ammonia-lyase (PAL) in the whole period of soybean plant growth . Therefore, the systematic and detailed research of mechanism on metabolism of soybean isflavone is meaningful in terms of theory and practice. The results as following,Flaviods could obviously scavenge superoxide ( O2 ) and hydroxyl( OH), and asignificant positive correlation was found to be present between scavenging rate and flaviods content in the reactive system.Soybean isoflavones distribution was investigated in vegetative growth period (four stages before seeding). The isoflavones in soybean seeds transferred from cotyledon to other organs and isoflavoids metabolized in organs with the growth ofsoybean plant. The results of variance analysis showed that there was no significant difference in the same organ of soybean varieties, but the difference was highly significant in different organs of same variety. The content of isoflavones in organs on the ground was much more than that of underground at the stage of coming out, and isoflavones in cotyledon was much more than in other tissues in the stage of seedling. And the isoflavones in leaves was much more than in other organ in the stage of strong sprount and anthesis.Soybean isoflavones accumulated mainly in seeds in reproductive growth period and isoflavones was transferred from leaves to seeds with the development of soybean seeds. The content of isoflavones in seeds got more and more with the development of seeds, and had a highly significant correlation between the days after flowering and water content in seeds. The study of isoflavones in leaves with the development of seeds showed that the content of isoflavones in leaves was much less than that in seeds. The correlation analysis showed there was marked negative correlation between them two.The activity of phenylalanine ammonia-lyase(PAL) in different organ before seeding has been studied. The results showed that the activity of PAL in leaves was higher than in other organs in the stage of seedling, strong sprout and anthesis. The difference is highly significant in organs in vegetative growth. The content of isoflavones and PAL activity in leaves both increased by degress, but they decreased progressively in stems, and little increase or decrease in roots from seedling to strong sprout to anthesis. The change tendency of isoflavones content just liked that of PAL activity. So PAL activity could decide the synthesis of isoflavones in the growth ofplant .In reproductive growth period, the activity of PAL both in leaves and in seeds had the same tendency of increasing first, then decreasing, and reached highest level at 39th day after flowering. PAL activity decreased and isoflavones content increased in the late period of seed development, this might be caused by residence time ofisoflavones accumulating. It is necessary to make further study.The accumulation of soluable protein and soluable sugar content also be studied. The results indicated that isoflavones increased with the accumulating of soluable protein, and there was marked positive correlation between them. Isoflavones content increased with soluable sugar content in early...
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