10 research outputs found
Allelopathy of Bracken Fern (Pteridium arachnoideum): New Evidence from Green Fronds, Litter, and Soil
The neotropical bracken fern Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae) is described as an aggressive pioneer plant species. It invades abandoned or newly burned areas and represents a management challenge at these invaded sites. Native to the Atlantic Forest and Cerrado (Tropical Savanna) Brazilian biomes, P. arachnoideum has nevertheless become very problematic in these conservation hotspots. Despite some reports suggesting a possible role of allelopathy in this plant’s dominance, until now there has been little evidence of isolated and individually identified compounds with phytotoxic activities present in its tissues or in the surrounding environment. Thus, the aim of this study was to investigate the allelopathic potential of P. arachnoideum by isolating and identifying any secondary metabolites with phytotoxic activity in its tissues, litter, and soil. Bioguided phytochemical investigation led to the isolation and identification of the proanthocyanidin selligueain A as the major secondary compound in the green fronds and litter of this fern. It is produced by P. arachnoideum in its green fronds, remains unaltered during the senescence process, and is the major secondary compound present in litter. Selligueain A showed phytotoxic activity against the selected target species sesame (Sesamum indicum) early development. In particular, the compound inhibited root and stem growth, and root metaxylem cell size but did not affect chlorophyll content. This compound can be considered as an allelochemical because it is present in the soil under P. arachnoideum patches as one of the major compounds in the soil solution. This is the first report of the presence of selligueain A in any member of the Dennstaedtiaceae family and the first time an isolated and identified allelochemical produced by members of the Pteridium species complex has been described. This evidence
of selligueain A as a putative allelochemical of P. arachnoideum reinforces the role of allelopathy in the dominance processes of this plant in the areas where it occurs
Alelopatia em Pteridium arachnoideum (Kaulf.) Maxon. (Dennstaedtiaceae)
Pteridium plants are ferns (monilopytes) distributed all around the globe. These plants are considered problem species as they invade recently abandoned or burned areas, and areas under anthropogenic impacts. In Brazil, Pteridium arachnoideum (Kaulf.) Maxon. has become an important problem species at the Cerrado (Tropical Savanna) and Atlantic Forest biomes. To understand the mechanisms underlying invasive plants success are one of the greatest challenges of the last decades. Among the interaction that can influence this success, we find allelopathy. However, untill now we have few evidences for this phenomenon on these plants, especially from the isolation and indentification of secondary metabolites with activities related to allelopathy. Therefore, the present work aimed to evaluate the allelopathy role by direct phytotoxicity and abiotic changes in Pteridium arachnoideum (Kaulf.) Maxon. dominance in the areas it invades. To do so, the bioguided phytochemical study of this plant tissues and litter was performed, as well as the evaluation of the phytotoxic activity of phenolic
compounds present in its litter and of its isolated and identified secondary metabolite against the early development of sesame, verifying the presence of this compound in the soil, its quantification, and evaluation of its interactions with physical and chemical soil characteristics. The phytochemical study led to the isolation and identification of a majoritarian compound in the plants green fronds and litter, the proanthocianidin selligueian A. This is the first time this compound is described for P. arachnoideum, as well as for the Dennstaediaceae family. Selligueain A showed phytotoxic activity against wheat coleoptiles elongation, with inhibitory activity over 71%, and IC50 of 0.69 mM. The poliphenols enriched fraction extracted from P. arachnoideum litter exert inhibitory activity against the early development of bioindicators species, native and invasive species of the Cerrado biome, specially over the development of these seedlings roots, besides activity against the metaxylem cells of sesame, and against chlorophyll content of sesame and the native weed Setaria parviflora. The allelopathic potential of the main poliphenolic compound of P. arachnoideum, selligueain A, was also evaluated against the early growth of sesame seedlings, promoting root and shoot growth in all the concentrations tested. Sesame seedlings grown in the presence of selligueain A showed smaller metaxylem cells when compared to the control, in the concentrations of 0.3 mM e 1 mM, with 50.82% inhibition in the greatest concentration and IC50 value of 0.98 mM. There was no activity of selligueain A against chlorophyll content of these seedlings. Analyses of extracts of soil collect under a P. arachnoideum patches pointed to the presence of selligueain A as major compound in soil solution, and, therefore, as a putative allelochemical produced by this plant. The concentration observed for this compound in the soil raged between 0.02 and 0.65 mM. According to allelopathic potential results, this concentration rage is sufficient to act over cooccurring plant species, promoting P. arachnoideum dominance. The presence of P. arachnoideum in Cerrado areas alters the chemical conditions of the soil, especially regarding N and Al, when compared to the presence of U. decumbens. Additionally, Al concentration is correlated to litter mass and to selligueain A concentration at the sites sampled. These results corroborates the hypothesis of allelopathy as a dominance mechanism of this plant in the areas where it occurs, with the first report of an allelochemical for a Pteridium species, by direct phytotoxic activity as well as by controlling Al concentration at those areas.Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Plantas do gênero Pteridium são samambaias (monilófitas) e estão distribuídas em todo mundo. São consideradas espécies problemas pois invadem áreas recentemente queimadas, abandonadas ou sob impacto antrópico. No Brasil, Pteridium arachnoideum (Kaulf.) Maxon. apresenta-se como uma importante espécie problema do Cerrado e da Mata Atlântica. Compreender os mecanismos que governam o sucesso de plantas com comportamento invasor tem se mostrado um dos maiores desafios das últimas décadas. Dentre as interações que podem influenciar este sucesso está a alelopatia. No entanto, poucas são as evidências apresentadas até então para este fenômeno, especialmente a partir do isolamento e identificação de substâncias do metabolismo secundário destas plantas. Assim, o objetivo deste trabalho foi avaliar o papel da alelopatia por fitotoxicidade direta e alterações abióticas na dominância de P. arachnoideum nas áreas em que ocorre. Para isso, foi realizado estudo fitoquímico biodirigido de diferentes órgãos e serrapilheira desta planta, avaliação da atividade fitotóxica dos polifenóis e do metabólito secundário isolado e identificado sobre o desenvolvimento inicial da espécie bioindicadora gergelim, identificação da presença deste composto no solo, sua quantificação e avaliação de sua interação com características físicoquímicas do solo. O estudo fitoquímico levou ao isolamento de um composto majoritário presente em suas frondes verdes e serrapilheira desta planta, a proantocianidina selligueina A. Esta é a primeira vez que este composto é descrito para P. arachnoideum, assim como para a família Dennstaediaceae. A selligueina A apresentou atividade fitotóxica sobre o alongamento de coleóptilos de trigo, com atividade inibitória acima de 71%, e IC50 de 0,69 mM. A fração enriquecida em polifenóis extraídos da serrapilheira de P. arachnoideum exerceu atividade inibitória sobre o desenvolvimento inicial de espécies bioindicadoras, nativa e invasora do Cerrado, especialmente sobre o desenvolvimento das raízes dessas plântulas, e atividade sobre as células do metaxilema de gergelim, e sobre o conteúdo de clorofila de gergelim e de capim rabo-de-raposa. O potencial alelopático do principal composto polifenólico desta planta, selligueina A, também foi testado sobre o crescimento inicial de gergelim, promovendo inibição do comprimento final do caule e da raiz de plântulas de gergelim em todas as concentrações testadas. Plântulas de gergelim crescidas na presença de selligueina A apresentaram células do metaxilema menores do que o as do controle nas concentrações de 0,3 mM e 1 mM, com inibição de 50,82% na maior concentração e IC50 de 0,98 mM. Não houve atividade de selligueina A sobre o conteúdo de clorofila dessas plântulas. Análises dos extratos de solo coletado sob manchas de P. arachnoideum apontaram a presença de selligueina A como composto majoritário na solução do solo, e, portanto, como aleloquímico produzido por esta planta. As concentrações do composto no solo variaram entre 0,02 e 0,65 mM. De acordo com resultados de potencial alelopático essa faixa de concentração seria suficiente para
potencialmente atuar sobre espécies co-ocorrentes, favorecendo a dominância de P. arachnoideum. A presença de P. arachnoideum em áreas de Cerrado altera condições químicas do solo, especialmente com relação à concentração do nutriente N e de Al, quando comparada à presença de braquiária (U. decumbens). Além disso, a concentração de Al se encontra correlacionada à massa de serrapilheira e à concentração de selligueina A nas áreas amostradas. Estes resultados corroboram a hipótese de alelopatia como mecanismo de dominância dessa planta nas áreas em que ocorre, com a primeira descrição de um aleloquímico para uma espécie do gênero Pteridium, que apresenta atividade não apenas por fitotoxicidade direta, mas também por ação indireta, ao controlar a concentração de Al nessas áreas
Relative frequencies (%) of the size classes of sesame (<i>S</i>. <i>indicum</i>) seedling root metaxylem cells treated with different concentrations of selligueain A.
<p>Relative frequencies (%) of the size classes of sesame (<i>S</i>. <i>indicum</i>) seedling root metaxylem cells treated with different concentrations of selligueain A.</p
Early growth inhibition<sup>a</sup> of sesame (<i>S</i>. <i>indicum</i>) seedlings treated with different concentrations of selligueain A.
<p>Early growth inhibition<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161670#t001fn003" target="_blank"><sup>a</sup></a> of sesame (<i>S</i>. <i>indicum</i>) seedlings treated with different concentrations of selligueain A.</p
Selligueain A isolated from green fronds and litter of <i>P</i>. <i>arachnoideum</i>.
<p>Selligueain A isolated from green fronds and litter of <i>P</i>. <i>arachnoideum</i>.</p
Chlorophyll a (C<sub>a</sub>), chlorophyll b (C<sub>b</sub>), and total chlorophyll (C<sub>a + b</sub>) contents<sup>a</sup> of photosynthetic cotyledons of sesame (<i>S</i>. <i>indicum</i>) seedlings treated with different concentrations of selligueain A.
<p>Chlorophyll a (C<sub>a</sub>), chlorophyll b (C<sub>b</sub>), and total chlorophyll (C<sub>a + b</sub>) contents<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0161670#t003fn002" target="_blank"><sup>a</sup></a> of photosynthetic cotyledons of sesame (<i>S</i>. <i>indicum</i>) seedlings treated with different concentrations of selligueain A.</p
HPLC-PDA chromatograms of the extracts of soil collected from under a <i>P</i>. <i>arachnoideum</i> patch.
<p>S: selligueain A standard; E1: ESQ-1 soil sample extract; E2: ESQ-2 soil sample extract; E3: ESQ-3 soil sample extract; E4: ESQ-4 soil sample extract; 1: selligueain A peak.</p
Inhibition of wheat (<i>T</i>. <i>aestivum</i>) coleoptile fragment elongation in the presence of the EtOAc extracts fractions of <i>Pteridium arachnoideum</i> green fronds and litter and the herbicide Logran in different concentrations.
<p>(A) and (B): Green frond fractions; (C): Litter fractions. Black columns, 0.8 mg.mL<sup>−1</sup>; gray columns, 0.4 mg.mL<sup>−1</sup>; white columns, 0.2 mg.mL<sup>−1</sup>. Vertical bars indicate standard deviation. Values marked with the letter a (<i>p</i> < 0.01) or b (0.01 < <i>p</i> < 0.05) are significantly different from those of the negative control according to Welch's test.</p
Micrographies of root metaxylem cells of sesame (<i>S</i>. <i>indicum</i>) seedlings.
<p>20× magnification.</p
Inhibition of wheat (<i>T</i>. <i>aestivum</i>) coleoptile fragment elongation in the presence of selligueain A isolated from <i>P</i>. <i>arachnoideum</i> or the herbicide Logran at different concentrations.
<p>Vertical bars show standard deviation. Values marked with the letter a (<i>p</i> < 0.01) and b (0.01 < <i>p</i> < 0.05) are significantly different from those of the negative control according to Welch's test.</p