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 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’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.

Through secondary metabolism, plants produce chemical compounds which when released into the environment can have effects on other species, such effect is called allelopathy. In this research we evaluated the Cordia oncocalyx (Boraginaceae) allelopathic potential against two weed species, Cenchrus echinatus and Calotropis procera, as well as quantified its phenolic compounds using HPLC-DAD. The experimental design was completely randomized with six treatments and one control group (distilled water). Each treatment consisted of four replicates with 25 seeds each, totaling 100 seeds per treatment. The variables analyzed were: germinating potential, germination velocity and seedling development. The hot and cold infusion extracts were prepared with 50 g of each of the three parts of the donor plant (bark, leaves and roots) immersed in 500 ml of distilled water at 100 °C (hot infusion) and 25 °C (cold infusion). The experiments were mounted in Petri dishes having substrate filter paper embedded in 3 mL of the extracts (treatments) and conducted in a germination chamber. Hot and cold infusion extracts of the C. oncocalyx leaves, barks and roots presented allelopathic activity on C. echinatus and C. procera germination and development, with the hot bark extract promoting such effect with a greater intensity. The allelopathic effect observed may be due to the presence of allelochemicals such as caffeic acid, quercentin and kaempferol present in C. oncocalyx leaves, barks and roots.

A alelopatia pode ser utilizada no combate às plantas daninhas, as quais podem interferir negativamente nos diversos ambientes naturais e cultivados. Entre as plantas daninhas existentes na Caatinga estão Calotropis procera e Cenchrus echinatus. Desta forma, objetivou-se, avaliar o efeito alelopático de extratos de folhas, caules e raízes de Ziziphus joazeiro na germinação e desenvolvimento das referidas espécies. Foram utilizadas duas porções de 50 g de cada parte da planta para 500 mL de H20 destilada. O experimento constou de seis tratamentos: extrato de folhas, caules e raízes a 100 °C (infusão) e a 25 °C (a frio), seguidos de um grupo controle (água destilada). Os parâmetros analisados foram: Porcentagem de germinação, Índice de Velocidade de Germinação e comprimento do caulículo e radícula. De modo geral, a porcentagem de germinação e o IVG das de C. echinatus foram afetados negativamente por todos os tratamentos testados. Com relação ao desenvolvimento de suas plântulas, houve uma interferência significativa no desenvolvimento das radículas. Em relação às sementes de C. procera, quando comparadas ao grupo controle, não houve nenhuma diferença estatística nem para a porcentagem de germinação nem para o IVG. Com relação ao desenvolvimento não houve interferência nem para o caulículo nem para a radícula, com exceção do Extrato por infusão a quente que inibiu o desenvolvimento do caulículo. Os resultados mostram que houve interferência alelopática mais eficiente sobre C. echinatus principalmente quando submetida ao extrato por infusão da casca da espécie doadora.