Abstract
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.
Highlights
The allelopathy, positive or negative interference of donor plant species on germination, initial growth or development of host species present in the same environment (Alves et al, 2004) is attributed to allelochemicals or phytochemicals (Rice, 1984; Ferreira & Borghetti, 2004; Rizzardi et al, 2008)
At the same time they would prevent serious damage to nature such as degradation and contamination of the water table due to the increasing use of chemicals (Carvalho et al, 2002). Considering these aspects, the objective of this study was to verify the effect of extracts by hot and cold infusion of leaves, stem bark and roots of Cordia oncocalyx on the germination and initial development of the plants of Cenchrus echinatus and Calotropis procera, and to identify the secondary compounds present in said extracts responsible for the observed effects
According to the HPLC-DAD spectra and (Table 1), the bark extracts present quercetin as its major polyphenolic compound, with the hot extract having a concentration of 5.97±0.01 mg/g and the cold extract 3.26±0.07 mg/g
Summary
The allelopathy, positive or negative interference of donor plant species on germination, initial growth or development of host species present in the same environment (Alves et al, 2004) is attributed to allelochemicals or phytochemicals (Rice, 1984; Ferreira & Borghetti, 2004; Rizzardi et al, 2008). It is important to note that in the present study, it was found that the presence of plant residues in the soil was associated with a higher level of plant depletion Such allelochemicals may affect respiration, photosynthesis, enzymatic activity, water relations, stomatal opening, hormone levels, mineral availability, cell division and stretching, structure and permeability of membranes and cell walls (Zeng et al, 2010). In the literature are attributed to leaves, barks and roots of the species Cordia one of the largest and most important genera of the Boraginaceae family, a great diversity of biological and pharmacological activities such as: antimicrobial, antifungal, larvicidal, antiinflammatory and analgesic (Medeiros et al, 2007; Matias et al, 2013), which may be related to different classes of secondary metabolites present in them.
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