RESUMO

Cladocerans are constantly exposed to humic substances in nature, yet the effects of these substances on their survival and reproduction are not well known. Here, the effects of humic substances (20 and 40 mg L-1) (HS) on the life history variables of three common cladocerans, Ceriodaphnia dubia, Moina macrocopa, and Daphnia pulex were evaluated. The results showed that the effect of humic substances on the tested cladocerans is species-specific, affecting either survival, reproduction or both. For M. macrocopa, exposed to HS at a concentration of 40 mg L-1, the average lifespan and the life expectancy at birth were significantly reduced as compared to controls, but for C. dubia and D. pulex these parameters were increased. Gross reproductive rate was unaffected by the HS level for both D. pulex and M. macrocopa, but it was significantly higher for C. dubia. When compared to the corresponding controls, for HS-exposed cladocerans, the rate of population increase was significantly reduced in case of D. pulex while it was stimulated for both C. dubia and M. macrocopa. It appears that humic substances had a slightly stronger influence on survivorship than on reproduction of the tested cladocerans.

Assuntos

RESUMO

Humic substances are organic compounds that possess high molecular weight and are formed by the decomposition of plant materials. Humic substances comprise humic acids, fulvic acids and humin. Humic acids (HA) have shown to be able to provide some protection to biological membranes of fish in water with low pH, replacing the protective action of Ca2+. Thus, this studyaimed to observe growth of silver catfish ( Rhamdia quelen ) juveniles exposed to pHs 5.5 and 6.5 and to different levels of HA: 0, 10, 25 and 50mg L-1. Results showed that, irrespective of pH, HA was highly detrimental to silver catfish growth, since the higher the concentration of HA, the lower the weight gain and feed intake, resulting in lower biomass and lower specific growth rate of juveniles. Hence, HA is extremely damaging to the performance of silver catfish juveniles in the tested concentrations.(AU)

Substâncias húmicas são compostos orgânicos que possuem elevado peso molecular e são formadas pela decomposição da matéria orgânica de plantas. As substâncias húmicas compreendem ácidos húmicos, ácidos fúlvicos e humina. Os ácidos húmicos (AH) têm mostrado serem capazes de proporcionar proteção parcial das membranas biológicas de peixes em águas com baixo pH, substituindo a ação protetora do Ca2+. Assim, este estudo teve como objetivo observar o crescimento de juvenis de jundiá ( Rhamdia quelen ) expostos a pH's 5,5 e 6,5 com diferentes níveis de AH: 0, 10, 25 e 50mg L-1. Os resultados demostram que, independentemente do pH, o AH foi altamente prejudicial para o crescimento do jundiá, uma vez que, quanto maior era a concentração de AH, menor era o ganho de peso e a ingestão de alimentos, resultando em menor biomassa e taxa de crescimento específico inferior dos juvenis. Assim, os AH são extremamente prejudiciais para o desempenho de juvenis de jundiá nas concentrações testadas.(AU)

Assuntos

RESUMO

This study evaluates whether humic acid (HA; Aldrich) protects the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), against exposure to acidic pH. Survival, levels of Na+, Cl- and K+ plasma, hematocrit, hemoglobin and erythrocyte morphometry were measured. Fish were exposed to 0, 10, 25 and 50 mg L 1 HA at four pH levels: 3.8, 4.0, 4.2 and 7.0 up to 96 hours. None of the fish exposed to pH 3.8 survived for 96 hours into the experiment, and survival of fish subjected to pH 4.0 decreased when HA concentration increased. Plasma Na+ levels decreased when pH was acidic, with no influence of HA, while Cl- levels declined at low pH with increased HA concentration. The levels of K+ at pH 4.0 and 4.2 increased without HA. Hematocrit and hemoglobin augmented under the effect of HA. At pH 4.0 and 4.2, erythrocytes of fish not exposed to HA were smaller, an effect that was partially offset by the presence of HA, since the values at pH 7.0 were higher. Although HA showed some positive effects changes in hematological and plasma K+ª in silver catfish caused by exposure to acidic pH, the overall findings suggest that HA does not protect this species against acidic pH because it increased mortality and Cl- loss at pH 4.0.(AU)

Assuntos

RESUMO

This study evaluates whether humic acid (HA; Aldrich) protects the silver catfish, Rhamdia quelen (Quoy & Gaimard, 1824), against exposure to acidic pH. Survival, levels of Na+, Cl- and K+ plasma, hematocrit, hemoglobin and erythrocyte morphometry were measured. Fish were exposed to 0, 10, 25 and 50 mg L 1 HA at four pH levels: 3.8, 4.0, 4.2 and 7.0 up to 96 hours. None of the fish exposed to pH 3.8 survived for 96 hours into the experiment, and survival of fish subjected to pH 4.0 decreased when HA concentration increased. Plasma Na+ levels decreased when pH was acidic, with no influence of HA, while Cl- levels declined at low pH with increased HA concentration. The levels of K+ at pH 4.0 and 4.2 increased without HA. Hematocrit and hemoglobin augmented under the effect of HA. At pH 4.0 and 4.2, erythrocytes of fish not exposed to HA were smaller, an effect that was partially offset by the presence of HA, since the values at pH 7.0 were higher. Although HA showed some positive effects changes in hematological and plasma K+ª in silver catfish caused by exposure to acidic pH, the overall findings suggest that HA does not protect this species against acidic pH because it increased mortality and Cl- loss at pH 4.0.

Assuntos

RESUMO

A aclimatização de mudas de orquídeas propagadas in vitro é um processo lento e que pode ser beneficiado com o uso de bioestimulantes, como, por exemplo, as substâncias húmicas. O presente trabalho objetivou estudar o crescimento de Cymbidium sp. em resposta à aplicação de ácidos húmicos extraídos de compostos orgânicos de cama de frango (AHcf) e de esterco bovino (AHeb) durante o período de aclimatização. As plantas micropropagadas foram imersas nas soluções de 0, 10, 20, 30 e 40mmol L-1 de C na forma de AHcf e de AHeb e aclimatizadas em viveiro. Aos 150 dias, as plantas foram coletadas para medição das variáveis: número de folhas, altura da planta, diâmetro do caule, matéria fresca da raiz e da parte aérea, matéria seca da raiz, da parte aérea e total, relação entre raiz:parte aérea. Os dados foram submetidos à análise de variância, contraste e análise de regressão. Os resultados mostraram incrementos no acúmulo de matéria seca total das plantas com a aplicação da concentração de 18,75mmol L-1 de C de AHcf e de 3,77mmol L-1 de C de AHeb, com incrementos em relação ao controle de 21 e 28%, respectivamente. Conclui-se que o uso dos ácidos húmicos nas doses indicadas acelera o crescimento das mudas propagadas in vitro de Cymbidium sp., favorecendo a diminuição do período necessário de aclimatização.(AU)

The acclimatization of in vitro propagated orchid is a slow process that can be benefited from the use of bio-stimulants, such as humic substances. This study investigated the growth of Cymbidium sp. in response to application of humic acids extracted from organic compounds poultry litter (AHcf) and manure (AHeb) during the acclimatization period. The plants were immersed in solutions of 0, 10, 20, 30 and 40mmol L-1 of C from AHcf and AHeb and acclimatized in a greenhouse. After 150 days, the plants were collected for measurement of variables: number of leaves, plant height, stem diameter, root and shoot fresh weight, root, shoot and total dry matter and root shoot ratio. Data were submitted to analysis of variance, regression analysis and contrast. The results showed increased accumulation of total dry matter of the plants with the application of concentration of 18.75mmol L-1 of C AHcf and 3.77mmol L-1 of C AHeb with increments in the control 21 and 28%, respectively. It is concluded that the use of humic acids at the indicated doses accelerates the growth of plantlets propagated in vitro of Cymbidium sp. favoring the reduction of time required for acclimatization.(AU)

Assuntos

RESUMO

A aclimatização de mudas de orquídeas propagadas in vitro é um processo lento e que pode ser beneficiado com o uso de bioestimulantes, como, por exemplo, as substâncias húmicas. O presente trabalho objetivou estudar o crescimento de Cymbidium sp. em resposta à aplicação de ácidos húmicos extraídos de compostos orgânicos de cama de frango (AHcf) e de esterco bovino (AHeb) durante o período de aclimatização. As plantas micropropagadas foram imersas nas soluções de 0, 10, 20, 30 e 40mmol L-1 de C na forma de AHcf e de AHeb e aclimatizadas em viveiro. Aos 150 dias, as plantas foram coletadas para medição das variáveis: número de folhas, altura da planta, diâmetro do caule, matéria fresca da raiz e da parte aérea, matéria seca da raiz, da parte aérea e total, relação entre raiz:parte aérea. Os dados foram submetidos à análise de variância, contraste e análise de regressão. Os resultados mostraram incrementos no acúmulo de matéria seca total das plantas com a aplicação da concentração de 18,75mmol L-1 de C de AHcf e de 3,77mmol L-1 de C de AHeb, com incrementos em relação ao controle de 21 e 28%, respectivamente. Conclui-se que o uso dos ácidos húmicos nas doses indicadas acelera o crescimento das mudas propagadas in vitro de Cymbidium sp., favorecendo a diminuição do período necessário de aclimatização.

The acclimatization of in vitro propagated orchid is a slow process that can be benefited from the use of bio-stimulants, such as humic substances. This study investigated the growth of Cymbidium sp. in response to application of humic acids extracted from organic compounds poultry litter (AHcf) and manure (AHeb) during the acclimatization period. The plants were immersed in solutions of 0, 10, 20, 30 and 40mmol L-1 of C from AHcf and AHeb and acclimatized in a greenhouse. After 150 days, the plants were collected for measurement of variables: number of leaves, plant height, stem diameter, root and shoot fresh weight, root, shoot and total dry matter and root shoot ratio. Data were submitted to analysis of variance, regression analysis and contrast. The results showed increased accumulation of total dry matter of the plants with the application of concentration of 18.75mmol L-1 of C AHcf and 3.77mmol L-1 of C AHeb with increments in the control 21 and 28%, respectively. It is concluded that the use of humic acids at the indicated doses accelerates the growth of plantlets propagated in vitro of Cymbidium sp. favoring the reduction of time required for acclimatization.

Assuntos