Allelopathic potential of extracts the from marine macroalga Plocamium brasiliense and their effects on pasture weed

Abstract

Four extracts from the marine red alga Plocamium brasiliense (Greville) M.A.Howe & W.R.Taylor were prepared to identify and characterize their potential allelopathic effects on seed germination, radicle elongation and hypocotyl development of the weeds Mimosa pudica L. and Senna obtusifolia (L.) Irwin & Barneby. The four extracts were prepared in a sequence of solvents of increasing polarity: n-hexane, dichloromethane, ethyl acetate and ethanol/water (7:3). The germination bioassay was carried out at 25 °C with a 12 h photoperiod and the radicle elongation and hypocotyl development at 25 °C with a 24 h photoperiod. The dichloromethane extract showed inhibitory effects on seed germination of both plants (35 and 14%, respectively, in M. pudica and S. obtusifolia), radical germination (52 and 41.7%, respectively) and hypocotyl development (17.1 and 25.5%, respectively). Given the high sensitivity of this parameter to the potential allelopathic effects and the insuffi cient number of references found in the literature, these results are expected to stimulate new tests with other species of marine algae. Given the high sensitivity of the method for the detection of allelopathic potential, the species P. brasiliense emerges as a possible source of allelopathic substances against weed species. The results are attributed to the chemical composition, especially in relation to the presence of halogenated monoterpenes.

Mevalonosomes: specific vacuoles containing the mevalonate pathway in Plocamium brasiliense cortical cells (Rhodophyta)

“…In an applied context, these molecules showed activity as herbicides (Fonseca et al. ) and against both herpes virus (Ferreira et al. , Pinto et al.…”

“…Although studies of the chemical ecology of P. brasiliense are scarce, it was demonstrated that P. brasiliense monoterpenes have high anti-herbivore activity Vasconcelos 2014). In an applied context, these molecules showed activity as herbicides (Fonseca et al 2012) and against both herpes virus (Ferreira et al 2010, Pinto et al 2014) and snake venom (Claudino et al 2014). Thus, the aims of the present work were: (i) to describe the ultrastructure of P. brasiliense CC using optical (OM), transmission (TEM), and scanning electron microscopy (SEM); (ii) to localize mevalonic acid enzyme activity inside CC by using a specific cytochemical assay; and (iii) to investigate the AF activity of P. brasiliense halogenated monoterpenes using in vitro bioassays.…”

Inhibitory Effects of the Lipophilic Extracts and An Isolated Meroditerpene of Brown Alga in Pasture Weeds in the Eastern Amazon Region

“…Since 2010, the marine natural product of Brazilian seaweeds have been studied for their effects on the seed germination, radicle elongation, and hypocotyl development of the weeds Mimosa pudica L., and Senna obtusifolia (L.) Irwin & Barneby, locally called "malícia" and "matapasto", respectively. In previous studies, researchers have demonstrated the inhibitory effects of the crude extract and different fractions of monoterpenes produced by the marine red alga Plocamium brasiliense (Greville) Howe & Taylor (Fonseca et al, 2012), as well as of a mixture of the diterpenes pachydictyol A and isopachydictyol A isolated from the acetone extract of the brown alga Dictyota menstrualis (Hoyt) Schnetter, Hörning, & Weber-Peukert (Fonseca et al, 2013). Their promising results have encouraged us to continue research with other extracts and natural products produced by marine algae.…”

“…Altogether, our results reveal that hexane and dichloromethane extracts from S. zonale have potent phytotoxic activity against M. pudica and S. obtusifolia. Comparative analysis of the phytotoxic bioassays on seed 69.00 (3.00) 37.00 (1.00) Other benthic seaweed extracts, including s hexane, dichloromethane, ethyl acetate, and ethanol-water extracts from the red seaweed Plocamium brasiliense (Fonseca et al 2012), as well as fractions and diterpenes isolated from the brown alga Dictyota menstrualis (Fonseca et al, 2013), have also achieved promising results against M. pudica and S. obtusiloba. Results obtained with the extracts, fractions, and natural products of benthic seaweeds underscore the importance of research to identify alternative weed inhibitor such as herbicides, as well as highlight seaweeds as a promising alternative for the management of weeds in pasture.…”

Allelopathic effect of essential oils of medicinal plants in Bidens pilosa L.

“…Nonetheless, these procedures have been demonstrated to be ineffi cient (Almeida, 1988;Souza Filho et al, 2006). Thus, synthetic herbicides currently used in agriculture, despite its importance for the control of weeds, there is extensive discussion of the damage they cause to both man and the environment (Fonseca et al, 2012).…”