Abstract
Plants that produce secondary metabolites with allelopathic activity or phytotoxicity can be biotechnologically important, serving as sources of allelochemicals, and thus contributing to the agroindustrial sector. Vismia japurensis (Hypericaceae) is an Amazonian species that grows in clumps called vismiais, from which most other plants are absent. Accordingly, the objective of this study was to identify possible phytotoxicity effects of hexane and methanol extracts of Vismia japurensis leaves and branches in vivo and from seedlings grown in vitro on Lactuca sativa. In addition, fresh and dry leaves were assayed by the sandwich method in order to determine their ability to release allelochemicals. The hexanic extract from in vitro seedlings reduced germination by 10%, while the methanol extract produced a 16% reduction in germination speed. Root growth of Lactuca sativa was inhibited by 64.7% when subjected to hexane leaf extract, by 39.3% under the influence of hexane branch extract, and by 96.09% for in vitro seedling hexanic extract. When analysed by thin layer chromatography and 1H nuclear magnetic resonance, extracts showed evidence of terpenes, anthraquinones and flavonoids, with greater intensity of signals in the aromatic region of in vitro seedling hexanic extract. Clearly, Vismia japurensis has a high biotechnological potential in terms of the production of substances of low polarity with capacity to interfere in plant development.
Highlights
The plant material of Vismia japurensis used for extract preparation from an adult specimen was collected at the Federal University of Amazonas (UFAM) campus in August 2017, under permits numbers: 16970-1 from IBAMA and AF64920 from SISGEN
The growth test, using the sandwich method, yielded no significant differences in L. sativa root growth, but a decrease was observed for aerial part growth of 22.31% and 19.43%, respectively, at concentrations of 40 and 60 mg for dry leaves; and 19.7%, 23.6% and 25% at concentrations of 20, 40 and 60 mg of fresh leaves, respectively
Since the sandwich test showed little or no growth interference, Vismia japurensis can be considered a phytotoxic but not allelopathic species. This agrees with results found for polar extracts of Vismia guianensis, where no allelopathic action was found on L. sativa and Solanum lycopersicum L germination and seedling growth (Almeida and Leone, 2017)
Summary
The management and development of appropriate technologies for biological weed control is a priority, since problems with undesired plant species in economically strategic crops can jeopardize the food supply and cause production-based financial losses (Agostinetto et al, 2015).Currently control of weeds is carried out using chemical and mechanical methods, either separately or in combination, sometimes causing serious damage to the environment (Spiassi et al, 2015), and in the case of mechanical control, it can be inefficient for species can establish and spread swiftly from vegetative fragments (Agostinetto et al, 2015). Obtaining bioherbicides of natural origin represents a biotechnological aim, since it could produce products that resolved the problem A variety of secondary metabolites can interfere with the establishment of other species, by influencing such aspects of plant development as germination and growth. Plants producing such chemicals under natural conditions are termed ‘allelopathic’ (Rice, 1974; Latif et al, 2017), but they can be considered ‘phytotoxic’, when their organic extracts are evaluated in the laboratory (Reigosa et al, 2013)
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