THE EFFECT OF PLANT-AGE AND NODULATION ON THE ISOFLAVONOID CONTENT OFRED-CLOVER (TRIFOLIUM-PRATENSE)

The effect of age and inoculation with nodulating bacteria on the isof lavonoid content of red clover (Trifolium pratense L.) has been determ ined. Both roots and foliage contained a complex range of conjugated i soflavonoids with formononetin-7-O-glucoside-6 ''-malonate (FGM), maac kian 3-O-glucoside-6 ''-O-malonate (MKGM), four acidic (presumed malon ylated) 7-O-glycosides of biochanin A (BGMs), and an acidic (presumed malonylated) glycoside of an unknown 5,7-dihydroxy-containing isoflavo noid metabolite termed UN 1GM being the major metabolites in all plant parts. In contrast, the concentrations of the corresponding isoflavon oid aglycones always remained low In the foliage, the order of abundan ce of the conjugates was FGM > BGM > UN 1GM > MKGM, while in the roots of plants up to 15 days old the order was FGM > BGM = MKGM > UN1GM, c hanging to MKGM > FGM > BGM > UN1GM in the older roots. In all plant p arts the concentrations of these various conjugates were affected diff erently by plant growth and nodulation. In the foliage, BGM, FGM and U N1GM increased with age and this accumulation was partially suppressed by nodulation. In uninoculated roots MKGM accumulated steadily with a ge, while overall the concentrations of FGM, BGM and UN1GM remained un changed. Nodulation suppressed the accumulation of MKGM and resulted i n a decline in FGM content. These results suggest that nodulation not only affects isoflavonoid accumulation in the roots but can also syste mically regulate isoflavonoid metabolism in the foliage.