Megaspore germination and initial development of Regnellidium diphyllum Lindman (Pteridophyta, Marsileaceae) sporophytes in the presence of cadmium

Abstract

-(Megaspore germination and initial development of Regnellidium diphyllum Lindman (Pteridophyta, Marsileaceae) sporophytes in the presence of cadmium). Regnellidium diphyllum has its distribution restricted to Southern Brazil and adjoining localities in Uruguay and Argentina. Currently it is on the list of threatened species of Rio Grande do Sul. The conversion of wetlands into agricultural areas or soil contamination by the introduction of waste products and fertilizers may compromise the establishment and survival of this species. Among the pollutants are heavy metals, such as cadmium (Cd). Megaspores were germinated in liquid culture medium, with concentrations 0 (control), 0.39; 0.78; 1.56; 3.12; 6.25; 12.5; 25; 50 and 100 mg L . In apomictical sporophytes, the growth of primary root and leaf was significantly reduced and no secondary leaf was formed at Cd concentrations of 12.5 and higher than this. The results indicated that R. diphyllum is tolerant to the presence of Cd up to considerably higher concentrations (0.78 mg L -1 ) than that normally found in unpolluted aquatic ecosystems (0.01 mg L -1 ), although the sensitivity to higher concentrations might endanger the establishment and permanence of this species in habitats exposed to contamination with this metal.Key words -ecophysiology, heavy metals, pollution, pteridophytes, reproduction RESUMO -(Germinação de megásporos e desenvolvimento inicial de esporófitos de Regnellidium diphyllum Lindman (Pteridophyta, Marsileaceae) na presença de cádmio). Regnellidium diphyllum tem sua distribuição restrita ao Sul do Brasil e localidades vizinhas no Uruguai e na Argentina. Atualmente, ela faz parte da lista de espécies ameaçadas do Rio Grande do Sul. A conversão de áreas úmidas em espaços para agricultura ou a contaminação do solo pela introdução de resíduos tóxicos e fertilizantes podem comprometer o estabelecimento e a sobrevivência da espécie. Entre os poluentes, estão metais pesados, como o cádmio (Cd). Megásporos foram germinados em meio de cultura líquido, com concentrações de 0 (controle), 0,39; 0,78; 1,56; 3,12; 6,25; 12,5; 25; 50 e 100 mg L . Em esporófitos apomíticos, houve redução significativa do crescimento da raiz e da folha primárias e ausência de formação de folha secundária a partir de 12,5 mg L -1 de Cd. Os resultados indicaram que R. diphyllum é tolerante à presença de Cd em concentrações consideravelmente mais altas (0,78 mg L -1 ) do que aquelas normalmente encontradas em ecossistemas aquáticos não poluídos (0,01 mg L -1 ), embora a sensibilidade a concentrações mais altas possa ameaçar o estabelecimento e a permanência dessa espécie em habitats expostos à contaminação com esse metal.Palavras-chave -ecofisiologia, metais pesados, poluição, pteridófitas, reprodução

Effects of nickel on the fern Regnellidium diphyllum Lindm. (Marsileaceae)

“…The growth reduction of roots and leaves of this species was recorded in previous in vitro experiments with other metals. Just as nickel, cadmium added to the culture medium at concentration of 50 mg L -1 resulted in a significant reduction of germination, and no germination was observed at 100 mg L -1 (Wunder et al, 2009). Growth of primary roots and primary leaves were significantly reduced in cadmium concentrations between 12.5 and 50 mg L -1 , and no secondary leaves were formed (Wunder et al, 2009).…”

“…Just as nickel, cadmium added to the culture medium at concentration of 50 mg L -1 resulted in a significant reduction of germination, and no germination was observed at 100 mg L -1 (Wunder et al, 2009). Growth of primary roots and primary leaves were significantly reduced in cadmium concentrations between 12.5 and 50 mg L -1 , and no secondary leaves were formed (Wunder et al, 2009). Decreased megaspore germination with subsequent sporophytic development was verified from 0.5 mg L -1 chromium (VI) concentration onwards, while growth of primary roots and primary and secondary leaves was significantly reduced in 3.2 mg L -1 concentration or higher (Kieling-Rubio et al, 2010).…”

“…The species grows in wetlands, the leaf lamina frequently floating and the rhizome developing in the humid soil or mud. Previous studies reported effects of heavy metals and other pollutants on the early development of R. diphyllum (Wunder et al, 2009;Cassanego et al, 2010;Droste et al, 2010;Kieling-Rubio et al, 2010).…”

Germination and sporophytic development of Regnellidium diphyllum Lindm. (Marsileaceae) in the presence of copper

“…Th e species is currently listed as "vulnerable" on the endangered species list of the state of Rio Grande do Sul (Rio Grande do Sul 2003). Considering the conservation status of this species as well as the continuous destruction and contamination of habitats, studies have been conducted to evaluate the eff ects of heavy metals and other pollutants on R. diphyllum (Wunder et al 2009;Cassanego et al 2010;Droste et al 2010;Kieling-Rubio et al 2010& 2012.…”

Germination and sporophytic development of Regnellidium diphyllum Lindman (Marsileaceae) in the presence of hexavalent chromium

“…Considering that natural environments are exposed to intense and continuous alterations and pollution due to human activities and that little is known about the sensitivity of Regnellidium diphyllum to contaminants (Wunder et al, 2009;Cassanego et al, 2010), megaspore germination and initial development of sporophytes in the presence of chromium were investigated in vitro in order to establish the species' tolerance limits to this contaminant, as well as to evaluate biological responses during the initial stages of the life cycle.…”