Effect of Arbuscular Mycorrhizal Fungus and the γ-Aminobutyric Acid Treatment in Nitrate Assimilation under Nitrogen Deficiency in Sorghum Plant

In this study, we investigated the synergistic effect of colonization plant roots by arbuscular mycorrhizal fungus (Glomus intraradices) (AMF) and the gamma-aminobutyric acid (GABA) treatment in nitrate uptake and assimilation under nitrogen deficiency (0.5 mM) in sorghum (Sorghum bicolor (L.) Monech) plants. Plants were treated under control or en presence of AMF, with or without 50 mg/L GABA. We found that the combination of GABA and AMF exhibited the highest shoot length and fresh weight with a maximum of chlorophyll content. In the same way, the key enzymes responsible for nitrogen and carbon metabolisms such as: glutamine synthetase (GS), glutamate synthase (GOGAT), glutamate dehydrogenase (GDH), nitrate reductase (NR), phosphoenolpyruvate carboxylase (PEPC), asparate aminotransferase (AAT) and isocitrate dehydrogenase (ICDH) show a very significant increase in the leaves and roots of mycorrhizal plants treated with GABA compared to control plants, plant treated with GABA or AMF alone with remarkable enhacement in roots AAT and ICDH activities being 4-fold and 6-fold respectively compared to the control plants. These results show that the combined effect of GABA and AMF under N deficiency which might lead to improvement in morphological growth of sorghum plant by enhacement of nitrogen uptake and assimilation.