Phytotoxic potential and chemical composition of Commelina benghalensis L. (Commelinaceae) on Lonchocarpus sericeus (Poir.) Kunth ex DC. (Fabaceae)

Abstract

The objective of this work was to verify the phytotoxic action of the aqueous extract of Commelina benghalensis, on the initial development of Lonchocarpus sericeus. The parameters analyzed were germination, Germination Speed Index (GVI), average length of the stem and radicle, morphoanatomical alterations, cytotoxic activity and phytochemical characterization of the donor species. The 100 % extract was prepared by grinding 250 g of fresh leaves of the donor species in 1 L of distilled water and diluted to 25 %, 50 %, 75 % concentration (Treatments), the control group 0 %, consisted of distilled water only. The bioassays were placed in a germination chamber of the type BOD (Biochemical Oxygen Demand) climate-controlled chambers with a constant temperature of 25 °C and a 12 h photoperiod (light/dark). The extract of C. benghalensis at 75 % and 100 % concentration promoted a negative phytotoxic action on the average length of the rootlets of L. sericeus. The length of the stems showed a reduction only at the 100 % concentration. A significant increase in the genotoxic effect of the extract at 75 and 100 % concentration was observed, with the presence of chromosomal bridges, chromosomal adhesion, chromosome loss, C-metaphase and absence of membrane. The treatments caused changes in the internal morphology of the plant tissues of the radicle, such as necrosis of the epidermis and vascular system and disorganization of the cortex tissues. The allelochemicals present in the extract of C. benghalensis, such as alkaloids, anthocyanins, anthocyanidins, chalcones, aurones, flavonones, flavonols, xanthones, catechins, flavonones, were probably responsible for the negative effect found on the mitotic index and on the development and organization from the radicle tissues of L. sericeus.