Estudos sobre a nutrição mineral do arroz: XXIV. Absorção e redistribuição do radiofósforo nas variedades L - 45, Dourado Precoce e Penatie

Root and leaf uptake of P32 was studied using upland rice cultivars, namely: L-45, Dourado Precoce and Penatie. Significant differences in absorption were observed among varieties. Except in the case of L-45 in_ tact plants were able to absorb more phosphorus than excised roots. The dual mechanism of absorption was observed, one operating within the range of 1-5 umoles in the external solution and the second one in that of 10² to 10(4) micromoles. When added to the solution of either monoammonium or diammonium phosphate urea increased foliar uptake. In the presence of the second source urea helped the transport to other organs of the plant. Highest rate of long distance transport was observed in the case of cv. Penatie, the lowest taking place in the variety Dourado Precoce.Foram observadas diferenças significativas na absorção do P32 em função do tempo de contacto para as cultivares L-45, Dourado Precoce e Penatie. Exceção feita no caso da L- 45 as plantas inteiras absorvem mais que as raízes destacadas. 0 mecanismo duplo de absorção atuou no caso das três variedades, uma na faixa de 1-5 umoles de H2PO-4 e outro na de 10² Cn a 10(4) umoles. A presença de uréia na solução aumenta a absorção do P fornecido por via foliar. Quando se empregou fosfato diamônico como fonte de fósforo houve maior transporte do elemento, em presença de uréia, da folha tratada para os outros órgãos da planta. 0 transporte foi maior no caso da cv. Penatie, sendo menor no caso da cv. L-45 e muito pequeno na variedade Dourado Precoce

Studies on the mineral nutrition of rice: XXIII. Evaluation of the nutritional status of cv. L-45

Rice plants were grown in complete and deficient nutrient solutions, with respect to macronutrients. Growth was affected by lack of N, P and Mg only. The concentration of the elements in dry matter, however, was affected by the treatments. Both leaf analyses and quick tissue tests showed to be adequate to show variations in mineral composition in response to the omission of either N, P on K from the substrate. Foliar nitrate reductase activity decreased when any element, except Ca (increase) was lacking.O arroz de sequeiro, cv. L-45, foi cultivado em solução nutritiva contendo todos os macro e micronutrientes e com omissão dos primeiros, um de cada vez. A falta dos elementos no substrato afetou o crescimento na seguinte ordem crescente: nitrogênio, fósforo e magnésio. Não se notou influência da omissão dos demais na produção de matéria seca, embora tivesse havido diminuição no teor do elemento na planta quando o mesmo foi fornecido em concentração menor na solução. Verificou-se através da diagnose foliar redução no teor de N, P e K quando os mesmos se achavam deficientes. Resultado análogo foi obtido ao se fazer teste rápido (spot teste) para nitrato, fosfato e potásio solúvel no tecido foliar. A atividade da redutase de nitrato foliar diminuiu como conseqüência de todos os tratamentos, exceto o menos Ca, ca so em que aumentou significativamente

Stable Carbon Isotopes δ13C as a Proxy for Characterizing Carbon Sources and Processes in a Small Tropical Headwater Catchment: Nsimi, Cameroon

Stream carbon fluxes are one of the major components in the global C cycle, yet the discrimination of the various sources of stream carbon remains to a large extent unclear and less is known about the biogeochemical transformations that accompany the transfer of C from soils to streams. Here, we used patterns in stream water and groundwater δ13C values in a small forested tropical headwater catchment to investigate the source and contribution from the soil carbon pools to stream organic and inorganic carbon behavior over seasonal scales. Stream organic carbon (DOC and POC) comes mainly from the upper rich soil organic carbon horizons and derived from total organic carbon (TOC) of biogenic source. The isotopic compositions δ13CTOC, δ13CDOC and δ13CPOC of these carbon species were very close (− 30‰ to − 26‰) and typical of the forested C3 vegetation. The relationship observed between DOC and log pCO2 and δ13CDIC indicated that besides the considerable CO2 evasion that occurs as DIC is transported from soils to streams, there were also other processes affecting the stream DIC pool. In-stream mineralization of DOC and mixing of atmospheric carbon had a significant influence on the δ13CDIC values. These processes which varied seasonally with hydrological changes represent the main control on DOC and DIC cycling in the wet tropical milieu. The rapid turnover of carbon on hillside soils, the transformation of TOC to DOC in wetland soils and further mineralization of stream DOC to DIC favor the evasion of C, making the zone a source of carbon to the atmosphere

Estudos sobre a nutrição mineral do arroz: XXII. Exigências nutricionais da variedade L-45 cultivada em solução nutritiva

Rice plants cultivar L-45, a mutant obtained by Dr. A. Ando, Piracicaba, were grown in nutrient solution until maturity. At intervals, fixed to coincide approximately with physiological stages of development, samples were taken for analysis of dry matter production and nutrients accumulation. It was verified that maximan rate of uptake occurred from 64 to 106 days after germination which corresponds to full tillering and beginning of maturation. Nutritional requirements obeyed the following depreasing order: macronutrients - N, K, Ca, P, Mg and S; micronutrients - Mn, Fe, Zn, Cu and B. Export of macronutrients occurred in the same order, were as in the case of micronutrients it was: Mn, Zn, Fe, Cu, and B.Em condições de solução nutritiva foram estudados os seguintes aspectos da nutrição mineral da cv. de arroz de sequeiro L-45, obtida pelo Dr. A. Ando (ESALQ-USP e CENA-USP, Piracicaba, SP, Brasil) através de mutação induzida; acumulação de matéria seca e de nutrientes durante ociclo; exigências nutricionais. Verificou-se que: a velocidade máxima de absorção dos elementos minerais ocorreu entre 64 e 106 dias depois da germinação (perfilhamento e maturação). A exigência nutricional obedeceu à seguinte ordem decrescente: N, K, Ca, P, Mg e S; Mn, Fe, Zn, Cu e B. A exportação como produto colhido obedeceu à ordem, também decrescente: N, K,P, Mg, Ca, S; Mn, Zn, Fe, Cu e B

Discharge–calcium concentration relationships in streams of the Amazon and Cerrado of Brazil : soil or land use controlled

Author Posting. © The Author(s), 2011. This is the author's version of the work. It is posted here by permission of springer for personal use, not for redistribution. The definitive version was published in Biogeochemistry 105 (2011): 19-35, doi:10.1007/s10533-011-9574-2.Stream discharge-concentration relationships are indicators of terrestrial ecosystem function. Throughout the Amazon and Cerrado regions of Brazil rapid changes in land use and land cover may be altering these hydrochemical relationships. The current analysis focuses on factors controlling the discharge-calcium (Ca) concentration relationship since previous research in these regions has demonstrated both positive and negative slopes in linear log10discharge-log10Ca concentration regressions. The objective of the current study was to evaluate factors controlling stream discharge-Ca concentration relationships including year, season, stream order, vegetation cover, land use, and soil classification. It was hypothesized that land use and soil class are the most critical attributes controlling discharge-Ca concentration relationships. A multilevel, linear regression approach was utilized with data from 28 streams throughout Brazil. These streams come from three distinct regions and varied broadly in watershed size (106 ha) and discharge (10-5.7 to 103.2 m3 sec-1). Linear regressions of log10Ca versus log10discharge in 13 streams have a preponderance of negative slopes with only two streams having significant positive slopes. An ANOVA decomposition suggests the effect of discharge on Ca concentration is large but variable. Vegetation cover, which incorporates aspects of land use, explains the largest proportion of the variance in the effect of discharge on Ca followed by season and year. In contrast, stream order, land use, and soil class explain most of the variation in stream Ca concentration. In the current data set, soil class, which is related to lithology, has an important effect on Ca concentration but land use, likely through its effect on runoff concentration and hydrology, has a greater effect on discharge-concentration relationships.This research was supported by grant #’s NCC5-686 and NNG06GE88A of NASA’s Terrestrial Ecology Program as part of the Large-scale Biosphere-Atmosphere Experiment in Amazonia (LBA-ECO) project

Variação espacial de cátions, ânions e variáveis físico-químicas no rio Solimões-Amazonas entre Manaus e Jutaí, bacia amazônica

Cátions e ânions majoritários são espécies químicas de grande importância nos diversos compartimentos aquáticos, porém, pouco abordados de forma exclusiva na bacia amazônica. Neste sentido, o objetivo deste estudo foi avaliar a dinâmica espacial de Na+, Ca2+, K+, Mg2+, Cl- e SO4 2- em um trecho do rio Solimões-Amazonas, levando-se em consideração a alcalinidade, potencial hidrogeniônico (pH), condutividade elétrica (CE), sólidos totais em suspensão (STS) e carbono orgânico total (COT). As coletas foram realizadas em maio, julho e setembro de 2012 em sete pontos na calha principal do rio Solimões-Amazonas e na foz de alguns dos principais tributários: rios Jutaí, Juruá, Japurá e Purus. Os cátions e ânions foram analisados por cromatografia de íons, STS por gravimetria, pH por potenciometria, alcalinidade por titulação potenciométrica, CE por condutimetria e o COT por oxidação catalítica por combustão. As concentrações médias dos cátions seguiram esta ordem Ca2+>Na+>Mg2+>K+ e dos ânions SO4 2->Cl-. De montante à jusante a tendência foi diminuição nas concentrações de cátions e ânions, das variáveis pH, CE, STS e alcalinidade, além do aumento das concentrações de COT. O presente estudo evidenciou mudanças nas características químicas sofridas pelo rio Solimões em seu curso. O aporte dos tributários pode ser apontado como um dos fatores responsáveis por essas modificações