Avaliação do potencial alelopático de Chloroleucon foliosum (Benth) G. P. Lewis sobre a germinação e crescimento inicial de alface

Abstract

Chloroleucon foliolosum(Benth.) G. P. Lewis is a native tree from Caatinga commonly known as "arapiraca" and important to the timber industry and in folk medicine. However, there are few studies aimed at the possible impactscaused by the plant residues when those are released into the environment. Thus, this work aimed to evaluate the allelopathic effect of C. foliolosumleaf and stem ethanolic extracts (EFCF and ECCF, respectively) on germination and initial growthof lettuce (Lactuca sativaL.) seedlings. After collectionof the plant material, the ethanolic extracts were prepared from 50% ethanol. The qualitative phytochemical characterization of EFCF and ECCF was performed according to the methodology of Matos (1997). Thegermination assay was performed in microenvironments consisting of previously sterilized Petri dishes containing filter paper as substrate, containing lettuce seeds. The extracts were tested in concentrations of 1 mg/L, 10 mg/L, 100 mg/L, 1000 mg/L and 10,000 mg/L, as well asthecontrolgroup (distilled water), performed inquadruplicate. After 7 days of germination, was performedthe radicles and aerial parts morphometry, and the calculation of the rate of germination (IVG). The means were submitted to one-way ANOVA followed by the Tukey test and the differences between the treatments were considered significant for the P value <0.05. For both extracts, concentrations equal to or greater than 100 mg/L of EFCF were able to negatively affect lettuce growth,according to the length of radicle and shoot and IVG when compared to control. In phytochemical prospecting, both extracts have alkaloids and tannins; saponins, anthraquinone and catechins in ECCF, and flavonoids and phenolic compounds in EFCF. Therefore,the compounds contained in the extracts can generate different responses, so that the literature indicates that certain alkaloids and some phenolic compounds may be cytotoxic, having their effect enhanced by the presence of saponins and tannins, which mayassociate with the cell wall and facilitate the entryof allelochemicals. Considering the importance of the development of new technologies for the use of Caatinga plants, the study withextracts of C. foliolosumshow high toxicity in the concentrations tested (except 1 mg/L of ECCF), so that the,increase in theconcentrationpotentializedthe effect.