Phytotoxicity of leaf aqueous extract of Rapanea umbellata (Mart.) Mez (Primulaceae) on weeds

Abstract

ABSTRACT. Allelopathic substances can be used to develop weed control alternatives based on natural products. The objective of this study was to compare the phytotoxic activity of aqueous leaf extracts of Rapanea umbellata with the toxicity of a synthetic herbicide on the germination and growth of weed species. The weeds species barnyard grass (Echinochloa crus-galli), wild poinsettia (Euphorbia heterophylla) and morning glory (Ipomoea grandifolia) were used. The effects of the aqueous leaf extract of R. umbellata at concentrations of 10% and 5% (g mL ) were compared to the control (distilled water) and to the synthetic herbicide oxyfluorfen. The average weed germination time was significantly lower (p < 0.05) in control than in extract and herbicide treatments. The herbicide had more significant effects than the extract on the initial growth of the aerial part. However, the initial growth of the root part was significantly more affected by the leaf extract than by the herbicide. The extract also caused many disorders in weed root anatomy. Therefore, the leaf aqueous extract of R. umbellata showed important results that indicate that it should be bioprospected and that its allelochemicals should be purified for the discovery of natural-origin herbicides.Keywords: allelopathy, germination, growth, initial length, oxyfluorfen.Fitotoxidade do extrato aquosos foliar de Rapanea umbellata (Mart.) Mez (Primulaceae) sobre plantas infestantes de culturas agrícolas RESUMO. Substâncias alelopáticas podem ser utilizadas para o desenvolvimento de produtos alternativos baseados em compostos naturais para o controle de espécies infestantes. O objetivo deste trabalho foi comparar o efeito do extrato aquoso foliar de Rapanea umbellata com um herbicida sintético sobre a germinação e o crescimento inicial de espécies infestantes das culturas agrícolas. As espécies infestantes estudadas foram: capim-arroz (Echinochloa crus-galli), amendoim-bravo (Euphorbia heterophylla) e corda-deviola (Ipomoea grandifolia). Os efeitos do extrato foliar aquoso de R. umbellata nas concentrações 10 e 5% (g mL -1) foram comparados com controle (água destilada) e o herbicida sintético oxifluorfem. O tempo médio de germinação das espécies infestantes foi significativamente menor (p < 0,05) no controle do que em extrato foliar e o herbicida. O comprimento da parte aérea foi significativamente mais afetado pelo herbicida do que pelo extrato. Porém, o comprimento da parte radicular foi mais afetado pelo extrato do que pelo herbicida. O extrato também causou vários tipos de danos na anatomia das raízes das infestantes. O extrato foliar de R. umbellata apresentou resultados promissores que indicam que deve ser bioprospectado e seus aleloquímicos purificados para a descoberta de novos herbicidas de origem natural.

Ultrastructural response of wheat (Triticumaestivum L.) lines to potential allelopathy of Alstoniascholaris (L.) R. Br. leaf extract

“…It indicates more tolerance to allelochemical extract as there was minimum damage to metabolically active tissues. Barkosky et al, (2000), Chai et al (2013) and Novaes et al (2013) reported similar findings.…”

Ecological phytochemistry of Cerrado (Brazilian savanna) plants

“…As observed by Keszei et al (2008), this family is known for the elevated concentration of terpenes in their leaves and for the strong qualitative and quantitative variation of such compounds among the taxon, populations and individuals. The results published by Imatomi et al (2013a) do not indicate grouping of bioactivity for the 15 studied species by a taxonomic approach. The most studied Myrtaceae genera were Eugenia L. (6 occurrences), Myrcia D.C. (5 occurrences), Psidium L. (4 occurrences) and Stryphnodendron Mart.…”

“…In all cases, tests were carried out on leaf extracts. Of the 15 species studied by Imatomi et al (2013a), 12 showed activity. Blepharocalyx salicifolius Kuth O. Berg, Psidium australe Cambess., Eugenia punicifolia (Kunth) DC., Myrcia multiflora DC.…”

Allelopathic Potential of Rapanea umbellata Leaf Extracts

“…The neotropical Brazilian savanna is of great interest from the chemical ecology (allelopathy) point of view, because this ecosystem has a marked seasonal climate [10], and the species grow in nutritionally poor soils [11]. Furthermore, very few studies have been carried out on the isolation, identification, and potential of secondary metabolites from plants of the Cerrado [12] [13].…”

“…Mez (Myrsinaceae) is an arboreal, evergreen species that grows in the Cerrado [16]. Recent preliminary studies on extracts from leaves, stems, and roots indicated that only R. umbellata leaves showed phytotoxic effects on infesting species [13]. This finding suggests an allelopathic interaction.…”