Considering the need to produce effective bioherbicides to control weeds and thus reduce the contamination of environments through the use of agrochemicals in control of these plants, the scientific community has been studying the allelopathic activity of several species of Caatinga, once studies indicate that some species of this biome presentind to have activity allelopathic about other plants. On this, the present study aimed to evaluate the allelopathic potential and phenolic composition of extracts of Libidibia ferrea Mart. ex Tul. on seed germination and seedling development of Calotropis procera (Aiton) WT Aiton. and Cenchrus echinatus L. For the allelopathy test, leaf, bark and root extracts, both hot (100 °C) and cold (25 °C), were used, followed by a control group (distilled H2O). Phytochemical prospecting was performed by High Performance Liquid Chromatography (HPLC). The results showed that the hot L. ferrea bark extract has allelopathic activity on C. procera and C. echinatus, which was observed in all parameters analyzed. The phytochemical results showed that L. ferrea extracts present several phenolic compounds which are possibly responsible for the results observed against the two weed species studied, with standing out Gallic acid, Catechin, Caffeic acid, Ellagic acid, and Quercetin. It is therefore necessary to isolate these compounds in view of a potential future use for L. ferrea extracts in the production of a bioherbicide.
The plants produce a variety of compounds that are not directly associated with their growth and are derived from their secondary metabolisms. Such compounds can be used in the formulation of bioherbicides, in the control of weeds. Among the chemical groups that most present allelopathic actions are the phenolic compounds which are present the flavonoids. A species rich in such compounds is Guapira graciliflora, which allows hypothesizing that it may present phytotoxic action. In this way, the objective of this research was to evaluate its phytotoxic action on the germination and growth of Cenchrus echinatus and Calotropis procera. For this purpose, aqueous extracts were prepared from fruits and leaves and applied to seeds of the species mentioned above. Pre and post germinative parameters were measured. Our results show that the extracts can retard the growth of the roots of C. echinatus and C. procera in a significant way (p <0.05), however it is not able to interfere in the number of germinated seeds or germinated seeds speed. The mechanisms of action of the allelochemicals may be related to inhibition of specific PSII sites or reduction of chlorophyll content. Guapira graciliflora presents allelochemicals in the constitution of its leaves and its fruits that affect the growth of the initial structures of C. echinatus and C. procera, with potential to be used as bioherbicides in the control of these weeds.
Acompanhando a dinâmica recente no modo de acumulação nacional, no qual o capital avança e se reproduz em espaços diferenciados de forma desigual, verifica-se uma fragmentação institucional da gestão metropolitana, facilitada pelos novos arranjos federativos proporcionados pela Constituição Federal de 1988, firmando-se, a partir daí, um conjunto de novas metrópoles regionais. Nesse contexto, foi instituída, através da Lei Complementar Estadual nº 78 de 2009, a Região Metropolitana do Cariri – RMC/Ce. Este ensaio propõe, portanto, apontar elementos sobre as centralidades urbanas da região, na perspectiva de refletir sobre as condições metropolitanas existentes na mesma. Reconhece-se, a partir das análises, que o processo de criação da RMC se dá muito mais influenciado por fatores políticos e necessidade de benefícios fiscais, do que o reconhecimento da existência de características metropolitanas. Destaca-se, ainda, o desafio imposto às políticas públicas para pensar o desenvolvimento local a partir de uma realidade regional onde são explícitas as assimetrias nos níveis de desenvolvimento socioeconômico entre os municípios.
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