Alemar Braga Rena

Growth periodicity in trees of Coffea arabica L. in relation to nitrogen supply and nitrate reductase activity

Abstract Vegetative growth of branches and leaf area gain in field-grown Arabica coffee trees in Vicosa, southeastern Brazil, exhibited active and quiescent phases. Nitrogen supplementation during the cool season did not prevent growth decline, nor did it alter the overall pattern of the tree growth; however, it enabled the plants to grow faster following the quiescent growth phase. Growth was related poorly to both nitrate content and nitrate reductase activity in leaves. In roots, N-fertilization in addition to accounting for greater content of nitrate, amino acids and ammonium was also associated with the maintenance of the nitrate reductase activity, but nitrate reduction was apparently nil in leaves during most of the cool season.

Effects of aluminum, nitrate and ammonium on the growth, potassium content and composition of amino acids in Stylosanthes

Se estudiaron en condiciones controladas los efectos de la interaccion entre el aluminio, nitrato y amonio, en solucion nutritiva. Se realizo un analisis sobre el crecimiento, las concentraciones de potasio y la composicion porcentual de N de los aminoacidos en Stylosanthes guianensis y S. macrocephala, sensibles y resistentes, respectivamente, tanto al aluminio y al amonio. El amonio redujo el crecimiento del S. guianensis drasticamente. La toxicidad de amonio, comprobada solo en el S. guianensis, estaba asociada con la estimulacion de la sintesis de las rutas metabolicas de la prolina y arginina, a partir del acido glutamico, en detrimento de la sintesis de glutamina. El aluminio alivia parcialmente la toxicidad de amonio en el S. guianensis, concomitante al aumento en la retencion de asparagina y reduccion en la composicion de arginina en el sistema de raices. En presencia de la fuente nitrica, el aluminio aumento las concentraciones de potasio solo en el S. macrocephala. En presencia de la fuente nitrica, la interconversion de N-aminico fue influenciada por el aluminio en ambas especies; sin embargo, la composicion porcentual de N-aminoacidos se modifico mas en el S. macrocephala.

Kinetics of phosphate absorption by Stylosanthes spp. in the presence of aluminium

Abstract The mechanisms of action by which aluminium affects phosphate absorption were evaluated in Stylosanthes guianensis (aluminium‐sensitive) and Stylosanthes macrocephala (aluminium‐tolerant), through kinetic studies with aluminium in pre‐ and co‐treatment. Multiphasic and cooperative models of ions absorption were tested. In the absence of aluminium, S. guianensis, a specie which normaly requires more phosphorus, showed lower rates of phosphate absorption, which was attributed to slower turnover of the carrier. In S. guianensis, the higher rates of absorption may be related to higher turnover and/or higher concentration of the carrier in the roots. Both species showed negative correlation in the absorption of phosphate, but it was more pronounced in S. guianensis. The effect of aluminium seems to be related to the decreased capacity of the carrier to associate with the ion. There may also be a reduction in the turnover of the carrier, which appears to be more pronounced in the tolerant species, redu...

Effects of aluminum, nitrate and ammonium on the metabolic nitrogened composition and of carboidrates in Stylosanthes guianensis and S. macrocephala

The effects of aluminum, nitrate and ammonium interaction, in nutritive solution, on the concentration of nitrogened compound, and of sugar in Stylosanthes guianensis and S. macrocephala, sensitive and tolerant, respectively, both to aluminum and to ammonium were studied under controlled conditions. The ammonium nutrition caused the appearance of toxicity symptoms of ammonium only in the S. guianensis. The ammonium source increased the concentrations of N-soluble, N-ammonium and N-amino acid mainly in the aerial part of the S. guianensis and in the root system of the S. macrocephala, while the total soluble sugar concentration increased in the aerial part of the S. guianensis and decreased in the root system of both species. The aluminum relieved partially the ammonium toxicity in the S. guianensis. When the nitrogen was supplied by the nitric source, the addition of the aluminum to the nutritive solution caused the appearance of symptoms of toxicity only in the S. guianensis. In the S. macrocephala, under the same conditions, an increase of total N, insoluble N, soluble N, nitric N and amino acid N in the aerial part and in the roots ocurred, followed by a decrease in the total soluble sugar concentration and sugar reductor in the roots.

Efeitos do alumínio, nitrato e amônio sobre a composição de metabólitos nitrogenados e de carboidratos em Stylosanthes guianensis e S. macrocephala

The effects of aluminum, nitrate and ammonium interaction, in nutritive solution, on the concentration of nitrogened compound, and of sugar in Stylosanthes guianensis and S. macrocephala, sensitive and tolerant, respectively, both to aluminum and to ammonium were studied under controlled conditions. The ammonium nutrition caused the appearance of toxicity symptoms of ammonium only in the S. guianensis. The ammonium source increased the concentrations of N-soluble, N-ammonium and N-amino acid mainly in the aerial part of the S. guianensis and in the root system of the S. macrocephala, while the total soluble sugar concentration increased in the aerial part of the S. guianensis and decreased in the root system of both species. The aluminum relieved partially the ammonium toxicity in the S. guianensis. When the nitrogen was supplied by the nitric source, the addition of the aluminum to the nutritive solution caused the appearance of symptoms of toxicity only in the S. guianensis. In the S. macrocephala, under the same conditions, an increase of total N, insoluble N, soluble N, nitric N and amino acid N in the aerial part and in the roots ocurred, followed by a decrease in the total soluble sugar concentration and sugar reductor in the roots.

Effects of aluminium, nitrate and ammonium on the composition of nitrogen metabolites and carbohydrates in Stylosanthes guianensis and S. macrocephala.

The effects of aluminum, nitrate and ammonium interaction, in nutritive solution, on the concentration of nitrogened compound, and of sugar in Stylosanthes guianensis and S. macrocephala, sensitive and tolerant, respectively, both to aluminum and to ammonium were studied under controlled conditions. The ammonium nutrition caused the appearance of toxicity symptoms of ammonium only in the S. guianensis. The ammonium source increased the concentrations of N-soluble, N-ammonium and N-amino acid mainly in the aerial part of the S. guianensis and in the root system of the S. macrocephala, while the total soluble sugar concentration increased in the aerial part of the S. guianensis and decreased in the root system of both species. The aluminum relieved partially the ammonium toxicity in the S. guianensis. When the nitrogen was supplied by the nitric source, the addition of the aluminum to the nutritive solution caused the appearance of symptoms of toxicity only in the S. guianensis. In the S. macrocephala, under the same conditions, an increase of total N, insoluble N, soluble N, nitric N and amino acid N in the aerial part and in the roots ocurred, followed by a decrease in the total soluble sugar concentration and sugar reductor in the roots.