L-3,4-Dihydroxyphenylalanine (L-DOPA) is an allelochemical released by roots of velvet bean (Mucuna pruriens) that affects the growth of several plant species. However, its mechanism of action is inconclusive. In this work, we compared the effects of L-DOPA (0.01-1.0 mmol L -1 ) and of aqueous extracts (300, 1200, and 3000 mg L -1 ) of velvet bean on growth and photosynthesis (gas exchange and chlorophyll a fluorescence) of soybean (Glycine max). Overall, the results showed that both L-DOPA and aqueous extracts of velvet bean reduced the growth, leaf area, photosynthetic rate (A), stomatal conductance (g s ), transpiration (E), and quantum yield of electron flow through photosystem II (PSII) in vivo (U F ). In addition, L-DOPA and aqueous extracts increased the internal CO 2 concentration (Ci) and the leaf wax and trichome density on the leaf surface, while the maximum quantum yield of PSII (F v /F m ) was not changed. These results suggest that the reduction of A should not be related exclusively to the stomatal closure, but also to limitations of the carbon metabolism, as indicated by the increase of Ci and decrease of U F . Briefly, we concluded that soybean growth inhibition by L-DOPA and aqueous extracts of velvet bean is due to the combination of damage in the root meristem and reduction in A.
Epidemiological studies have been investigating the relationship between chlorination byproducts exposure and cancer. Studies showed the incidence of colon, rectum and bladder cancer in laboratory animals when halogenated byproducts were administered to them, such as trihalomethanes. Based on this fact, in this work, two data sets of water quality parameters were analyzed with focus on total trihalomethanes (THMt). These two data sets are from two different time periods (one in 2014 and other in 2017). All the samples were collected in the same months, in both data sets. The samples were taken from its same corresponding sampling points in both periods of time. Trihalomethanes (THMs) are undesired byproducts of chlorination and its formation occurs when the chlorine used in water treatment reacts with natural organic matter, which is present in natural waters, during the disinfection process. The aim of this research was to investigate the THMs levels in storage water from the chlorination performed by the Water Treatment Station (WTS) of the Maringá-Parana-Brazil; also, to compare the results obtained with the maximum allowable values (MAVs) established by the Consolidation Resolution n.05/2017, current law of water quality in Brazil. Water samples were collected in eight high and fundamental schools of Maringá-Paraná-Brazil and analyzed through the gas chromatography method by the use of mass spectrometry detector with purge-and-trap concentrator (GC-MS) for THM. Furthermore, parameters such as pH and residual chlorine were analyzed following the methodology proposed by the Standard Methods for the Examination of Water and Wastewater. The study results to THMt show that the maximum value of 21.5 µg/L obtained is within the MAV of 100 µg/L. Chloroform was
Planta invasora de difícil controle, o picão-preto (Bidens pilosa L.) pode ser encontrado em quase todo o Brasil, inclusive nas áreas agrícolas ocupadas com espécies olerícolas, como a alface (Lactuca sativa L.). O controle das plantas invasoras tem sido realizado principalmente pelo uso de herbicidas, promovendo impacto ambiental e risco a saúde humana e animal. Assim, o objetivo deste trabalho foi avaliar o potencial alelopático do extrato aquoso de folhas secas de Eucalyptus grandis Hill ex Maiden sobre a germinação e o crescimento inicial de alface e picão-preto. Foram analisadas quatro concentrações do extrato aquoso (25, 50, 75 e 100%), além da testemunha (0%). O delineamento experimental foi inteiramente casualizado, com três repetições de cada tratamento, constituídas por 50 sementes de alface ou picão-preto distribuídas em gerbox e mantidas em câmara tipo B.O.D com fotoperíodo de 12h a 25ºC por 7 dias. Os resultados obtidos indicaram que Eucalyptus grandis Hill ex Maiden não apresentou potencial alelopático em relação às plântulas de picão-preto e a baixas concentrações pouco influenciou a germinação e o crescimento inicial de plântulas de alface.
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