Allelopathy and Allelochemicals of Eragrostis plana (Poaceae) and its Relation with Phenology and Nitrogen Fertilization

Abstract

-This study was conducted in order to verify if the phenological stage and the nitrogen fertilization interfere in the allelopathic activity and in the concentration of potentially allelopathic phenolic compounds of tough lovegrass (Eragrostis plana). The assay consisted of a bifactor 3 (0.100 and 200 kg N ha -1 ) x 2 (harvested in vegetative and reproductive stages), in a split plot design. The N doses constituted the main plot and the phenological stage during the harvest the subplots, resulting in six treatments. The tough lovegrass plants derived from each of the treatments were subjected to allelopathy bioassays, in which aqueous extracts of the aerial parts were applied to lettuce cypselae (Lactuca sativa) and to phytochemicals tests when ethanolic extracts were used, with subsequent partition with ethyl acetate, followed by a high-performance liquid chromatography analysis. There was nitrogen x phenological stage interaction on biological and chemical attributes. The allelopathic extracts were, in descending order of inhibition of germination, those from plants harvested at the vegetative stage and fertilized with 100 kg N and at the flowering stage with 200 kg N, which showed the highest catechin concentrations. The caffeic, ferulic, p-coumaric and vanillic acids were in a higher concentration in flowered and fertilized plants with 0 or 200 kg N. The management of the nitrogen fertilization and the harvesting age influence the allelopathic activity and the phytochemical composition of tough lovegrass.Keywords: germinability, phenolic acids, catechin, epicatechin. RESUMO -Este estudo foi realizado com o objetivo de verificar se a fenologia e a adubação nitrogenada interferem na atividade alelopática e na composição fenólica do capim-annoni (Eragrostis plana

Allelopathic potential of Cover Crops in Control of Shrubby False Buttonweed (Spermacoce verticillata)

“…Radicle sensitivity to allelopathic effect may occur due to the direct contact with the allelochemicals in the studied straws. As the first structure to appear after germination, the roots are exposed to allelochemicals, facilitating the absorption and action of allelopathic substances in the early stages of development (Zhang et al, 2016), thus interfering directly with cell division, compromising radicle elongation (Ferreira and Aquila, 2000) or even death of tissues (Cecchin et al, 2017). Chlorogenic acid, ferulic acid, catechin and p-anisic acid, all phenolic compounds, are reported as having a significant effect on the plant root system, acting on membrane stability and lignin synthesis with growth impairment of this plant organ on weeds (Carvalho et al, 2014;Cecchin et al, 2017).…”

“…As the first structure to appear after germination, the roots are exposed to allelochemicals, facilitating the absorption and action of allelopathic substances in the early stages of development (Zhang et al, 2016), thus interfering directly with cell division, compromising radicle elongation (Ferreira and Aquila, 2000) or even death of tissues (Cecchin et al, 2017). Chlorogenic acid, ferulic acid, catechin and p-anisic acid, all phenolic compounds, are reported as having a significant effect on the plant root system, acting on membrane stability and lignin synthesis with growth impairment of this plant organ on weeds (Carvalho et al, 2014;Cecchin et al, 2017). These results are important indicators of the allelopathic potential of cover crops, since sharp root reduction can affect the competitive capacity and the negative effect of the weed on the agricultural crop (Almeida et al, 2015).…”

“…These substances, called allelochemicals, derive from secondary metabolites and may promote negative effects on weed physiology as well as influence population dynamics in whole agroecosystems (Zhang et al, 2016). Physiological conditions influence these allelochemicals, such as nutritional and phenological stages, and the conditions of the environment where the plants are grown (Cecchin et al, 2017). Thus, studies of factors influencing the production and release of allelochemicals should be carried out in order to promote allelopathy as a non-conventional control resource for pest management in agricultural systems (Kobayashi and Ikato-Noguchi, 2015).…”

Interferência entre plantas daninhas e a cultura: alterações no metabolismo secundário

“…A concentração e o potencial alelopático podem ser alterados de acordo com a dose de nitrogênio e o estádio de coleta da planta. Plantas adubadas com 200 kg de nitrogênio apresentaram a maior concentração de ácidos cafeico, ferúlico, vanílico e p-cumárico quando comparados a dose de 100 kg, bem como a maior concentração destes ácidos foi encontrada no estádio reprodutivo do capim annoni (Cecchin, et al, 2017).…”

“…O extrato aquoso de folhas de capim anonni sobre trevo branco apresenta maior potencial alelopático quando comparado ao extrato de raízes (Favaretto et al, 2011). Logo, para doses de nitrogênio e estádio fenológico do capim annoni, as doses de 100 e 200 kg e o estádio reprodutivo aumentam a inibição da germinação e reduzem o índice de velocidade de germinação (Cecchin, et al, 2017).…”