Effect of low pH on the Enzyme Activities of the Ammonium Assimilation Pathways in the Symbiotic Association Bradyrhizobium sp-Peanut (Arachis hypogaea L.).

TERZO, E.; NATERA,V.; ISOLA, M.; FABRA,A.; FRANZONI,L.; CASTRO,S.

SYMBIOSIS

Año: 2005 p. 1 - 6

0334-5114

The activities of glutamine synthetase (GS, E.C. 6.3.1.2), glutamate synthase (GOGAT, E.C.1.4.1.13) were determinated in leaves, stems, roots and nodules of the peanut plants inoculated with the Bradyrhizobium sp SEMIA 6144 and grown in soils with neutral reaction (pH 7.0) or acid reaction (pH 5.5). Leaves, stems and nodules showed no significant differences in those activities between the different trial groups.  On the contrary, a high increase in the activities of the same enzymes was observed in inoculated roots as compared to non-inoculated one. The maximum increase of the specific activity of GS and GOGAT was registered in inoculated roots grown in soils with acid reaction.  Since inoculation and low pH of soil were necessary for a maximum in the activity of the ammonium assimilation enzymes, we can suggest that Bradyrhizobium sp strain is the part of the symbiotic association most sensitive to soil acidity.