Fixação e reações de assimilação de N em Crotalaria juncea L

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

Crotalaria juncea L. is a legume widely used as green manure. The objective of this work was to obtain basic information on the influence of the N-NH/ in the growth and production of nitrogen compounds and enzymes involved in nitrogen assimilation in this species. The responses of plants, inoculated (I) or not (NI) with Rhizobium to the presence (+N) or absence (- N) of NH/ were evaluated. The experiments were carried out in a greenhouse, in pots with vermiculite irrigated with nutrient solution containing (NH/)zSO4 in order to supply 20 mg of N/plant.week or with nutrient solution deprived of N. AlI the evaluations were carried out with 60 day old plants. Biological nitrogen fixation was not affected by _ +, since in the presence of this ion nitrogenase activity was not inhibited and shoots, roots and nodules ftesh and dry mass increased. GS activity was higher in leaves than in roots, in alI the treatments. Leaves ofNIl+N plants presented higher GS and GDH activities than ofI/+N plants. GS activity ofleaves, roots and nodules ofinoculated plants (+N or - N) was similar. However, GDH specific activity was higher in I/-N plants leaves and roots and in I/+N plant nodules. Independent of the treatment, GOGAT -NADH activity in leaves was almost null and the predominant form of the enzyme was that dependent of ferredoxin (GOGAT-Fd). In general, +N plant leaves presented higher pigment (total chlorophyl and carotenoids), total N and amino acids concentration. -N plants, that are fully dependent on Nz fixation, showed xylem sap with bigger amino acid contents than plants of other treatments, while +N plants presented nodules with bigger amino acid concentration. In general, differences between the treatments were not observed, as regards the ammonia content in the differents parts of the planto The levels of ureides found were minimum, confirming that the transport of nitrogen compounds in xylem sap of C. juncea is based on amino acids and ammoma

ASSUNTO(S)

crotalaria simbiose amonio

ACESSO AO ARTIGO

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