ATIVIDADE DA ENZIMA REDUTASE DE NITRATO EM TRÊS ESPÉCIES DE CAMPOS FERRUGINOSOS (CANGA) RESPONDE A FERTILIZAÇÃO NITROGENADA

AUTOR(ES)

Jane Eyre Casarino

DATA DE PUBLICAÇÃO

2009

RESUMO

Human activities have increased considerably the input of nitrogen in soils of agricultural and natural systems, may cause profound changes in physiology, morphology and ecology of plants. In this context, the activity of nitrate reductase (NR) becomes an important tool for understanding plant responses to increased N availability in soils through atmospheric deposition, since it is the key enzyme in N metabolism and proves very responsive to its substrate. This study was conducted in an area of field ferruginous rock system (canga) characterized by low availability of N, of the Universidade Federal de Ouro Preto, MG. We selected 10 individuals from three species belonging to functional groups of high, intermediate and low NR activity, respectively, Eremanthus incanus (Less.) Less., Byrsonima variabilis A. Juss. and Matayba marginata Radlk. For each species, individuals were divided into two groups: control and treatment, which consists of monthly additions of ammonium nitrate, totaling an increase of 30 kg N ha-1year-1. Real and potencial activities NR in vivo were measured monthly from color reaction for quantification of nitrite. Also were measured in individuals allometric, concentration of N and P foliar, retranslocation rates, SLA, leafs number and quantification of atmospheric deposition of nutrients in the study area. The vegetation of the canga presented species with different abilities to use the nitrate, and E. incanus, showed the highest value for the activity of the enzyme nitrate reductase, followed by M. marginata and B. variabilis; there were no positive correlations between leaf N content and activities of nitrate reductase; between increasing the amount of nitrogen in the foliar concentration of N and efficiency of N retranslocation during leaf senescence and not with increasing specific leaf area or number of leaves. For the species M. marginata and B. variabilis noted that the response of real activity responded more readily, at least some months of the study, the deposition of N, than the changes in morphology, concentration and rate of retranslocation of leaf N, which even succeeded in proving differences between the treatment and control groups during the study. Therefore, one may infer that these species NR activity was more sensitive indicators of early and nitrogen pollution than the methods traditionally used (morphological changes, retranslocation rates, etc.). For the E. incanus, there were no changes in NR activity and in none of the traditional parameters. Further studies should be performed, preferably longer than that of this work, to the other factors, such as mycorrhizal associations and more detailed characteristics of the soil, among others, might be considered, which may provide more specific results to this ecosystem, so, can be perceived more clearly the effect of N addition in that environment.

ASSUNTO(S)

field ferruginous rock system deposição atmosférica de nitrogênio atmospheric deposition of nitrogen canga fertilização nitrogenada nitrogen fertilization nitrate reductase activity canga. campos ferruginosos ecologia atividade de redutase de nitrato

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