Efeito do alumínio e de diferentes proporções de NO3-/NH4+ sobre o crescimento e os teores de P, K, Ca e Mg em dois cultivares de arroz
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2001-03-06
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Universidade Federal de Viçosa
Resumo
Este trabalho teve como objetivo analisar alguns aspectos da tolerância ao Al em dois cultivares de arroz: Maravilha (sensível: CNA-6843-1) e Fernandes (tolerante: CNA-1158), em solução nutritiva. Num primeiro experimento, plantas dos dois cultivares foram expostas ao Al em soluções nutritivas com diferentes proporções de NO 3- :NH 4+ e avaliados os efeitos do Al sobre o crescimento das plantas e sobre a liberação de H + para a solução nutritiva. Independente da proporção NO 3- :NH 4+ , tanto o comprimento quanto a produção de matéria seca de raízes e parte aérea diminuíram na presença de Al, nos dois cultivares, principalmente no sensível. O cultivar tolerante mostrou-se mais eficiente no consumo de H + quando o N disponível estava exclusivamente na forma nítrica. O sensível, entretanto, mostrou-se mais eficiente na liberação de H + para a solução nutritiva quando o N foi fornecido sob duas formas ou exclusivamente na forma amoniacal. Num segundo experimento, as plantas dos dois cultivares foram expostas a duas concentrações de Al e avaliados seus efeitos sobre os teores, as taxas de absorção líquida e os índices de eficiência de utilização de alguns elementos minerais, nas duas partes das plantas. Na presença de Al as plantas apresentaram teores mais elevados deste elemento nas duas partes da planta, principalmente nas raízes. O cultivar tolerante mostrou-se mais eficiente na retenção deste elemento nas raízes. Na presença de Al, observou-se redução nos teores de todos os elementos minerais estudados, tanto nas raízes como na parte aérea, exceto no de Ca nas raízes e no de K na parte aérea, do cultivar tolerante. De modo geral, as reduções nos teores destes elementos minerais foram mais intensas no cultivar sensível, nas duas partes das plantas. As taxas de absorção líquida, sofreram reduções crescentes com os níveis de Al na solução nutritiva, tendo o cultivar tolerante apresentado, de modo geral, taxas mais elevadas para todos os elementos minerais estudados. O efeito do Al sobre os índices de eficiência de utilização dos elementos minerais estudados foi variado. No cultivar tolerante, observou-se aumento nos índices de eficiência de utilização de P, Ca e Mg, permanecendo inalterado o de K. No cultivar sensível, os índices de eficiência de utilização de P e K diminuíram, o de Ca permaneceu inalterado e o de Mg aumentou. Na ausência de Al os cultivares não diferiram entre si quanto a estes índices, mas na presença deste elemento, seus valores foram, de modo geral, mais elevados no cultivar tolerante.
The objective of this work was to study some aspects of Al tolerance in two rice cultivars: Maravilha (sensitive: CNA-6843-1) and Fernandes (tolerant: CNA:1158), grown in nutrient solution. In a first experiment, plants of the two cultivars were exposed to Al in nutrient solutions with different NO 3- :NH 4+ proportions and the Al effects on plant growth and on H + exsudation to the nutrient solution were evaluated. Independent of the NO 3- :NH 4+ proportion, both the length and dry matter yield of roots and shoots decreased in Al presence, in both cultivars, mainly in the sensitive. The tolerant cultivar showed higher efficiency in the H + consumption in nutrient solution with the nitric form. The sensitive, however, showed higher the N exclusively in efficiency in the exudation of H + to the nutrient solution, when N was supplied in both N forms or exclusively in the ammonium form. In a second experiment, plants of both cultivars were exposed to two Al concentrations and its effects on the contents, on the net absorption rates and on the use efficiency indices of some mineral elements, were evaluated in both parts of the plants. In Al presence the plants exhibited increased contents of these element in both parts of the plant, mainly in the roots. The tolerant cultivar was more efficient in the Al retention in the roots than the sensitive one. In Al presence, the contents of all mineral elements decreased in both roots and shoots, except the content of Ca in the roots and of K in the shoots, of the tolerant cultivar. In general, the reductions in the mineral contents were stronger in the sensitive cultivar, in both parts of the plants. The net absorption rates reductions increased with Al levels in the nutrient solution. The tolerant cultivar, in general, exhibited higher absorption rates of all mineral elements studied. Aluminum effect on the use efficiency indices was quite variable. In the tolerant cultivar, the use efficiency indices of P, Ca and Mg increased and of K remained unaffected. In the sensitive cultivar, the use efficiency indices of P and K decreased, of Ca remained unaffected and of Mg increased. In Al absence there was no difference between cultivars with respect to these indices, but in the presence of this element, the tolerant cultivar showed higher values.
The objective of this work was to study some aspects of Al tolerance in two rice cultivars: Maravilha (sensitive: CNA-6843-1) and Fernandes (tolerant: CNA:1158), grown in nutrient solution. In a first experiment, plants of the two cultivars were exposed to Al in nutrient solutions with different NO 3- :NH 4+ proportions and the Al effects on plant growth and on H + exsudation to the nutrient solution were evaluated. Independent of the NO 3- :NH 4+ proportion, both the length and dry matter yield of roots and shoots decreased in Al presence, in both cultivars, mainly in the sensitive. The tolerant cultivar showed higher efficiency in the H + consumption in nutrient solution with the nitric form. The sensitive, however, showed higher the N exclusively in efficiency in the exudation of H + to the nutrient solution, when N was supplied in both N forms or exclusively in the ammonium form. In a second experiment, plants of both cultivars were exposed to two Al concentrations and its effects on the contents, on the net absorption rates and on the use efficiency indices of some mineral elements, were evaluated in both parts of the plants. In Al presence the plants exhibited increased contents of these element in both parts of the plant, mainly in the roots. The tolerant cultivar was more efficient in the Al retention in the roots than the sensitive one. In Al presence, the contents of all mineral elements decreased in both roots and shoots, except the content of Ca in the roots and of K in the shoots, of the tolerant cultivar. In general, the reductions in the mineral contents were stronger in the sensitive cultivar, in both parts of the plants. The net absorption rates reductions increased with Al levels in the nutrient solution. The tolerant cultivar, in general, exhibited higher absorption rates of all mineral elements studied. Aluminum effect on the use efficiency indices was quite variable. In the tolerant cultivar, the use efficiency indices of P, Ca and Mg increased and of K remained unaffected. In the sensitive cultivar, the use efficiency indices of P and K decreased, of Ca remained unaffected and of Mg increased. In Al absence there was no difference between cultivars with respect to these indices, but in the presence of this element, the tolerant cultivar showed higher values.
Descrição
Palavras-chave
Alumínio, Tolerância, Cultivar, NO3-/NH4+
Citação
MENDONÇA, Renilton Joaquim de. Efeito do alumínio e de diferentes proporções de NO3-/NH4+ sobre o crescimento e os teores de P, K, Ca e Mg em dois cultivares de arroz. 2001. 59 f. Dissertação (Mestrado em Fisiologia Vegetal) - Universidade Federal de Viçosa, Viçosa. 2001.