SOME PHENOLIC-COMPOUNDS ENHANCE NODULATION AND NITROGEN-FIXATION IN ASOYBEAN BRADYRHIZOBIUM-JAPONICUM SYSTEM

The present study has been carried out to clarify the effect of type, concentration and method of application of phenolic compounds (p-hydro xybenzoic acid, o-dihydroxybenzene, and 1,3,5-trihydroxybenzene) on no dulation, plant growth and total plant nitrogen. Phenolic compounds le vels of 10,100 and 1000 muM were applied in two different modes; spray ing of the shoots system and application with the irrigation solution. This study revealed that the three classes of phenols (mono-, di-and tri-) each at concentrations of 100 muM significantly increased nodula tion, plant dry matter and total plant nitrogen when applied with the irrigation solution. At this concentration, 1,3,5-trihydroxybenzene si gnificantly increased nodule NADH-GOGAT, NADH-GDH activities and total soluble protein. However, mono- and di-phenols caused only a slight i ncrease in the total activities of these enzymes and in protein. The p romotive effect of phenolic compounds at lower concentrations, on nodu le formation, plant growth and enzymes of ammonia-assimilation are pro mising for using these substances to enhance the nitrogen status of so ybean.