Cellulase activity and dissolved organic carbon release from lignocellulose macrophyte-derived in four trophic conditions

Abstract Considering the importance of lignocellulose macrophyte-derived for the energy flux in aquatic ecosystems and the nutrient concentrations as a function of force which influences the decomposition process, this study aims to relate the enzymatic activity and lignocellulose hydrolysis in different trophic statuses. Water samples and two macrophyte species were collected from the littoral zone of a subtropical Brazilian Reservoir. A lignocellulosic matrix was obtained using aqueous extraction of dried plant material (≈40 °C). Incubations for decomposition of the lignocellulosic matrix were prepared using lignocelluloses, inoculums and filtered water simulating different trophic statuses with the same N:P ratio. The particulate organic carbon and dissolved organic carbon (POC and DOC, respectively) were quantified, the cellulase enzymatic activity was measured by releasing reducing sugars and immobilized carbon was analyzed by filtration. During the cellulose degradation indicated by the cellulase activity, the dissolved organic carbon daily rate and enzyme activity increased. It was related to a fast hydrolysable fraction of cellulose that contributed to short-term carbon immobilization (ca. 10 days). After approximately 20 days, the dissolved organic carbon and enzyme activity were inversely correlated suggesting that the respiration of microorganisms was responsible for carbon mineralization. Cellulose was an important resource in low nutrient conditions (oligotrophic). However, the detritus quality played a major role in the lignocelluloses degradation (i.e., enzyme activity) and carbon release.

Xylanase and cellulase activities during anaerobic decomposition of three aquatic acrophytes

Enzymatic activity during decomposition is extremely important to hydrolyze molecules that are assimilated by microorganisms. During aquatic macrophytes decomposition, enzymes act mainly in the breakdown of lignocellulolytic matrix fibers (i.e. cellulose, hemicellulose and lignin) that encompass the refractory fraction from organic matter. Considering the importance of enzymatic activities role in decomposition processes, this study aimed to describe the temporal changes of xylanase and cellulose activities during anaerobic decomposition of Ricciocarpus natans (freely-floating), Oxycaryum cubense (emergent) and Cabomba furcata (submersed). The aquatic macrophytes were collected in Óleo Lagoon, Luiz Antonio, São Paulo, Brazil and bioassays were accomplished. Decomposition chambers from each species (n = 10) were set up with dried macrophyte fragments and filtered Óleo Lagoon water. The chambers were incubated at 22.5ºC, in the dark and under anaerobic conditions. Enzymatic activities and remaining organic matter were measured periodically during 90 days. The temporal variation of enzymes showed that C. furcata presented the highest decay and the highest maximum enzyme production. Xylanase production was higher than cellulase production for the decomposition of the three aquatic macrophytes species.

Toxidez por ácido acético em arroz sob diferentes valores de pH da solução nutritiva / Acetic acid toxicity in rice under different pH values of nutritional solution

A proporção das formas associadas e dissociadas do ácido acético é dependente do pH. O aumento do pH favorece a dissociação do ácido acético, o que pode diminuir seu efeito tóxico para o arroz, pois moléculas com carga são menos solúveis nos componentes lipídicos das membranas celulares. O objetivo deste trabalho foi determinar os efeitos do pH da solução nutritiva referentes à toxidez pelo ácido acético em plantas de arroz. O experimento foi conduzido em solução nutritiva, em bancada de laboratório com fornecimento de luz artificial. Os tratamentos foram dispostos em um fatorial 4x2, em delineamento inteiramente casualizado, com três repetições, e foram testados os fatores: pH da solução nutritiva (3,7; 4,7; 5,7; 6,7) e ácido acético (testemunha sem ácido e 2,5mmol L-1 de ácido). O incremento nos valores de pH de 3,7 a 6,7 reduziu o efeito tóxico do ácido acético nas plantas de arroz, aumentando o comprimento da raiz em 90 por cento e da parte aérea em 37 por cento. Houve aumento nos teores de N em 22 por cento e diminuição nos teores de Ca em 19 por cento na mesma faixa de pH na presença do ácido acético. Os efeitos tóxicos do ácido acético sobre as plantas de arroz foram atenuados com o aumento do pH de 3,7 para 6,7.

The proportion of forms associated and undissociated acetic acid depends on pH. The increment of pH induced the dissociation of acetic acid that may reduce the toxicity of rice, therefore, molecules with charge are less soluble in lipidics components of cellular membranes. The research objective was to estimate the effect of different pH values in nutritional solution on toxicity of acetic acid on rice. The experiment was conducted in nutritional solution in laboratory with artificial light supplied. The treatments were arranged in factorial 4x2, in completely randomized design, with 3 replications, where the following factors were tested nutritional solution pH (3.7; 4.7; 5.7 and 6.7) and acetic acid (zero and 2.5mmol L-1 of acid). The increment on pH values from 3.7 to 6.7 reduced the toxic effect of acetic acid in rice plants, increasing the radicular system in 90 percent and shoot in 37 percent. It increased the N content in 22 percent and reduction on Ca content in 19 percent in plants in same values of pH on presence of acetic acid. The toxic effect of acetic acid in rice plants were attenuated with pH increment from 3.7 to 6.7.

Changes in the amount of soluble carbohydrates and polyphenols contents during decomposition of Montrichardia arborescens (L) Schott / Variação dos teores de carboidratos e de polifenóis solúveis durante a decomposição de Montrichardia arborescens, (L) Schott

This study describes the aerobic and anaerobic decay of soluble carbohydrates (CH) and polyphenols (PH) during decomposition of Montrichardia arborescens. Plant and water samples were collected in the Cantá stream (2º 49' 11" N and 60º 40' 24" W), Roraima, Brazil. Decomposition chambers with plant fragments and stream water were incubated. Particulate organic matter was separated from dissolved organic matter and concentrations of CH and PH were determined. The results were fitted to 1st order kinetics models. CH and PH comprised a labile fraction (LCH and LPH) and a refractory fraction (RCH and RPH). The global coefficient associated with LCH weight loss was 1.4 times higher under aerobic conditions (3.4 day-1) higher than for anaerobic conditions. On the other hand, the RCH decay rate in the anaerobic process (0.0074 day-1) was 1.39 times higher. LCH was estimated to be 92 percent while RCH amounted to 8 percent. The LPH anaerobic decay was 5.2 times the value for the aerobic decay (0.67 day-1). For both conditions, RPH decay coefficients were similar (¼ 0.011 day-1). In the aerobic experiments LPH and RPH corresponded to 92.5 percent and 7.5 percent, respectively. For the anaerobic process these contents were 85.5 percent and 14.5 percent, respectively. From these results, we concluded that in the Cantá stream, the anaerobic degradation of phenols is more efficient than the aerobic counterpart. The aerobic condition provides a faster decay of carbohydrates of this plant.

Este estudo descreveu o decaimento aeróbio e anaeróbio de carboidratos (CH) e polifenóis (PH) durante a decomposição de Montrichardia arborescens. As amostras de planta e de água foram coletadas no igarapé do Cantá (2º 49 ' 11 " N e 60º 40 ' 24 " W), Roraima, Brasil. Câmaras de decomposição contendo fragmentos de plantas e água do iguarapé foram incubadas. A matéria orgânica particulada foi separada da dissolvida e as concentrações CH e PH foram determinadas. Os resultados foram ajustados a um modelo cinético de 1ª ordem. O CH e o PH apresentaram duas frações: uma lábil (LCH e LPH) e uma refratária (RCH e RPH). Verificou-se que o coeficiente global relacionado com a perda de massa do LCH para condição aeróbia (3,4 dia-1) foi 1,4 vezes mais elevado que para a anaeróbia. Por outro lado, o coeficiente de decaimento do RCH para o processo anaeróbio (0,0074 dia-1) foi 1,39 vezes mais elevado. O LCH foi estimado em 92 por cento e o refratário em 8 por cento. A degradação anaeróbia de LPH foi 5,2 vezes mais elevada que a aeróbia (0,67 dia-1). Os coeficientes de decaimento do RPH foram similares (¼ 0,011 dia-1) para ambas condições. Para o experimento aeróbio, o LPH e o RPH corresponderam a 92,5 por cento e 7,5 por cento. Para os processos anaeróbios estas frações foram de 85,5 por cento e 14,5 por cento, respectivamente. A partir destes resultados, supõe-se que no igarapé do Cantá, a degradação anaeróbia dos polifenóis seja mais eficiente que a aeróbia. A condição aeróbia promove um decaimento mais rápido dos carboidratos desta planta.

Occurrence of physiological disease in flooded rice fields / Ocorrência de bico de papagaio em arroz irrigado

The aim of this report is to desenhe the occurrence of the physiological disease "Parrot beak" in flooded rice grown in Rio de Janeiro state soils. The symptoms occurred particularly in the presence of decomposing organic material, affecting the yield because of the high percentage of sterile spickelets.

O objetivo deste trabalho é relatar a ocorrência da doença fisiológica Bico de Papagaio em arroz irrigado cultivado em solos do Estado do Rio de Janeiro. Os sintomas manifestaram-se significativamente na presença de material orgânico em decomposição afetando o rendimento de arroz, dada a elevada percentagem de espiguetas estéreis.