Through this study, the objective was to contribute to the knowledge regarding floristic composition, classification and conservation status of the studied plant species as well as the dispersion syndromes of flora found in a disjoint Cerrado area ​in the Chapada do Araripe, Crato-CE. For the research development Rapid Survey method, applied in three walking lines (Line 1, Line 2 and Line 3) was adopted. Floriferous branches, fruits and seeds from species in the study area were collected in order to identify them and to characterize their diaspores, in view of fitting them into the corresponding dispersion syndromes. A total of 103 species were identified, the richest species taxa were: Fabaceae, Apocynaceae, Euphorbiaceae, Malpighiaceae and Myrtaceae. The most abundant species in the studied area were: Cordiera myrciifolia (“bola”) Miconia albicans (“Candeiro-de-pelo”), Caryocar coriaceum (pequi) and Copaifera langsdorffii (“pau d'oleo”). Three new occurrences were also recorded for the state of Ceará: Eriope tumidicaulis, Myrciaria cf. tenella and Stachytapheta cf. crassifolia. The most frequent dispersion syndrome was zoochoria, followed by anemocoria. Considering that most of the species occurring in the study area have their dispersion diaspores transported by a fauna element, the importance of these species for the maintenance of the observed floristic richness is evident.

Chemical compounds from the secondary metabolism of a plant, termed as allelochemicals, may interfere with the germination and/or development of other plant species, a phenomenon known as allelopathy. The aim of this study was to analyze the allelopathic potential of the Senna cearensis Afr. Fern. aqueous extract at various concentrations, collected from an area in the Chapada do Araripe during two different seasons (dry and rainy), on Lactuca sativa L. and Cenchrus echinatus L. seeds and seedlings, in addition to analysing the extract’s phytochemical prospection. The bioassays were conducted in a germination chamber at 25 °C with a 12h photoperiod and consisted of four treatments (extract at 12.5%, 25%, 50% and 100%) and a control group (distilled water). The variables analyzed were: seed germination, germination speed index, radicle length and caulicle seedling length. The means from each variable were submitted to an analysis of variance and compared using Tukey’s test (p<0.05), through the ASSISTAT. Quantitative prospection of the extract was performed using HPLC-DAD. The extracts reduced L. sativa seed germination, however it did not affect C. echinatus seeds. The extracts caused a reduction in germination rate and presented inhibitory effects on seedling development for both receptor species. Quercitrin was the major compound in both extracts. The allelopathic activity of the S. cearensis aqueous leaf extract collected during dry or rainy periods may be a viable alternative for weed control. Further studies addressing fractionation for separation and the possible isolation of substances responsible for the observed allelopathic activity are necessary.

The use of cactus for forage may cause soil contamination by allelochemicals in order to compromise the future planting or even reforestation of that site. The objective of this work was to evaluate the allelopathic action of cladodes and roots of Cereus jamacaru, Pilosocereus gounellei and Tacinga inamoena on the germination and development of Cenchrus echinatus and Calotropis procera in order to suggest actions that increase efficiency in restoration strategies. Of the species of Cactaceae mentioned above, cladodes and roots were collected for the preparation of the extracts in which two types of extracts were prepared for each organ, one treatment by hot infusion and one cold treatment. Germination Percentages (GP) and Germination Speed Index (GSI) were analyzed. In order to analyze if the extracts presented some allelopathic activity regarding the development of the seedlings, the lengths of the stem and the radicle of the recipient species were measured. The results of this research show that cacti don&rsquo;t significantly affect GP from seeds of other plants. However, for GSI, roots and cladodes of T. inamoena presented negative allelopathic activity for C. echinatus and C. procera, respectively. In addition to GSI, T. inamoena negatively affected the development of C. echinatus rootlets. In this way T. inamoena is a forage cactus that affects the development of the initial structures of surrounding plants. Thus, the exacerbation of this forage species in natural areas should be avoided, since the released allelochemicals can interfere with the ecological succession of the plant species of that environment.

The present study aims to test the Acritopappus confertus (Gardner) R. M. King & H. Rob. essential oil allelopathic potential on the germination and inital development of Cenchrus echinatus L. and Lactuca sativa L. seedlings, in addition to identifying and quantifying chemical constituents. The chemical composition analysis was performed by gas chromatography (GC-FID) and gas chromatography coupled to mass-spectrometry (GC-MS). For the allelopathic assays, the essential oil was emulsified with dimethylsulfoxide (DMSO) in a 1:1 ratio, and diluted in distilled water to obtain 0.001, 0.01, 0.10, 0.25, 0.50, 0.75 and 1% c. The control consisted of 1% aqueous DMSO solution.Treatments were performed in five repetition with 20 seeds each. The pH of the oils were measured and adjusted to a scale of 6 to 7. Assays were conducted in a germination chamber at 25 °C with a 12h photoperiod. Seed germination, Germination Speed Index (GSI), caulicle and radicle length were analyzed. The data were subjected to analysis of variance and the means were compared by Tukey test (p<0.05), through the ASSISTAT. The constituents mycene, β-pinene and limonene stood out the most in chemical analysis. The essential oil did not influence C. echinatus and L. sativa seed germination, however it influenced GSI and seedling development. The effects observed herein may be due to chemical constituents found in the studied species, which may act in an isolated or combined manner.