Atividade alelopática e compostos fenólicos de plantas daninhas pelo método sanduíche

Abstract

Allelopathy is a mechanism of biochemical interaction between plants, considered as a form of chemical defensive adaptation of plants. In this phenomenon, secondary metabolites produced by a plant are released into the environment and influence the growth and development of neighboring plants. The objective of this work was to investigate the allelopathic potential of Alternanthera tenella, Paspalum maritimum, Priva bahiensis, Richardia grandiflora, Scoparia dulcis and Solanum paniculatum (donor species) through germination and initial development bioassays, as well as to identify and quantify phenolic compounds produced by these plants. The experiment was arranged in a completely randomized design with 4 receptor plants and 5 concentrations (0.00, 0.01, 0.02, 0.04 and 0.08 g), with 6 replicates of 15 seeds each. The seeds of Lactuca sativa, Emilia fosbergii, Portulaca oleracea and Digitaria insularis (recipient species) were planted to germinate in agar layers, in multiwell plates and kept in a growth room with constant temperature (25 ºC) and 12-hour photoperiod, for a period of 7 to 14 days. At the end of this period, germination percentage (PG), shoot length (CPA) and root length (CPR) were evaluated. The phenolic compounds were determined by high performance liquid chromatography (HPLC) and according to the methodology adopted and the results obtained it was possible to verify that all weed species tested have an allelopathic effect in the recipient plants of this study, but Paspalum maritimum e Scoparia dulcis were the most prominent allelopathic species in the tested plants and the polyphenols (caffeic acid, coumarin, salicylic acid, quercetin and kaempferol), leachate from the leaves and roots to the agar layers, in the higher concentration treatments, may be related with this allelopathic potential interfering in the percentage of germination, in the primary root growth and in the hypocotyl elongation of the seedlings of the host species.