The effects of the Azospirillum brasilense and Azospirillum lipoferum inoculation on the enzymes involved in ammonium metabolism in maize roots.

RIBAUDO CLAUDIA; RONDANINI DÉBORAH; TRINCHERO GUSTAVO; CURÁ ALFREDO; FRASCHINA ADELA

Vancouver, Canada

Congreso; Annual Meeting of American and Canadian Associations of Plant Physiologists; 1997

American and Canadian association of plant Physiologists

Plant with Azospirillum spp. can result in a significant change in various plant growth parameters, which may affect the crop yield. Bacteria of genus Azospirillum has been suggested as an alternative or a supplement to chemical fertilization. Ammonium is assimilated into glutamine and glutamate through the combined action of GS (EC 6.3.1.7) and Fd-GOGAT (EC 1.4.7.1) or NADH-GOGAT (EC 1.4.1.14). Another enzyme, glutamate dehydrogenase (GDH, EC 1.4.1.2) is considered involved in the ammonium assimilation. In maize, all these enzymes are found in the leaves and roots. The biochemistry of maize roots colonized by Azospirillum has not been extensively studied. The purpose of this work was to evaluate the effects of Azospirillum brasilense strain 42M and A. lipoferum strain 242 inoculation 108 CFU/ml on the roots NADH-GDH activity and GS activity. Experiments were performed under greenhouse condition, using pots culture containing vermiculite:sand (2:1). Plants (Hybrid Dekalb D664) were grown for 45 days, and the number of replications was 25. The enzymatic activities of root extracts were determined approximately once a week during a period of six weeks. Our results showed that GDH activity was higher in inoculated plants with Azospirillum, comparing with controls, and was similar to the fertilized control (10 mM NH4NO3), at the second week after sowing. The protein patterns were examined by SDS-PAGE, and new protein bands were observed in inoculated plants. The results obtained suggest that Azospirillum increase the activity of enzymes involved in the assimilation of nitrogen. More studies have to be performed to understand this interaction plant-microbe.