RESUMO
AIMS: This study aims at evaluating the ability of Beijerinckia derxii, a free-living nitrogen (N)-fixing bacterium frequently isolated from tropical soils, to release certain plant growth regulators [indoleacetic acid (IAA), ethylene, polyamines] and amino acids into the growth medium. METHODS AND RESULTS: The production of those substances was compared using both cultures in which nitrogenase was active (N-free medium) and cultures in which nitrogenase was repressed (combined-N cultures). Those cultures were grown under agitation and in absence of agitation. Total IAA production was higher in agitated, N-free cultures but specific production was greater in combined-N cultures under agitation. Putrescine and spermidine were detected under all conditions tested. Ethylene was produced in both N-free and combined-N cultures. A greatest diversity of amino acids was released in N-free cultures. CONCLUSIONS: There was no inhibition of the production of the analysed substances under conditions where nitrogenase was inactive. SIGNIFICANCE AND IMPACT OF THE STUDY: Beijerinckia derxii is potentially a producer of plant-active substances; its presence in the natural environment suggests that this bacterium may contribute to the development of other living organisms.
Assuntos
Aminoácidos/metabolismo , Beijerinckiaceae/metabolismo , Nitrogenase/metabolismo , Reguladores de Crescimento de Plantas/biossíntese , Microbiologia do Solo , Meios de Cultura , Etilenos/biossíntese , Ácidos Indolacéticos/metabolismo , Poliaminas/metabolismo , Putrescina/análise , Espermidina/análiseRESUMO
AIMS: To investigate the ability of Azospirillum sp., a facultative endophitic diazotrophic bacterium, to release plant growth regulators (PGR) such as polyamines, ethylene, indoleacetic acid and amino acids in both combined-N and N-free cultures. METHODS AND RESULTS: The presence of those substances was analysed by HPLC. Azospirillum sp. is capable of releasing PGR and amino acids into the culture medium. CONCLUSIONS: The type and quantity of the released substances varied, depending on the presence of combined-N in the medium. SIGNIFICANCE AND IMPACT OF THE STUDY: A better knowledge of PGR produced by Azospirillum sp. has been gained.