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

Abstract

The heterosporous fern Regnellidium diphyllum occurs in southern Brazil and some adjoining localities in Uruguay and Argentina. Currently it is on the list of threatened species in the state of Rio Grande do Sul. Anthropic alterations such as the conversion of wetlands into agricultural areas or water and soil contamination by pollutants may compromise the establishment and survival of this species. Nickel (Ni) is an essential nutrient for plants but increasing levels of this metal due to pollution can cause deleterious effects especially in aquatic macrophytes. Megaspore germination tests were performed using Meyer's solution, at concentrations of 0 (control), 0.05, 0.5, 1, 5, 10, 20, 30, 50 and 100 mg L -1 of Ni. The initial development of apomictic sporophytes was studied using solutions containing 0 (control) to 4.8 mg L -1 of Ni. A significant negative relation was observed between the different Ni concentrations and the megaspore germination/ sporophyte formation rates. Primary roots, primary leaves and secondary leaves were significantly shorter at 3.2 and 4.8 mg L -1 of Ni, when compared with the treatment without this metal. At 4.8 mg L -1, leaves also presented chlorosis and necrosis. The introduction of pollutants with Ni in the natural habitat of Regnellidium diphyllum may inhibit the establishment of plants in the initial stage of development, a problem to be considered in relation to the conservation of this species.Keywords: heavy metals, megaspore, germination, sporophyte, pollution. Efeitos do níquel sobre a filicínea Regnellidium diphyllum Lindm. (Marsileaceae) ResumoA samambaia heterosporada Regnellidium diphyllum Lindm. ocorre no Sul do Brasil e em algumas localidades vizinhas no Uruguai e na Argentina. Atualmente, consta da lista de espécies ameaçadas do Estado do Rio Grande do Sul. Alterações antrópicas -tais como a conversão de áreas úmidas em áreas de agricultura ou a contaminação de água e solo por poluentes -podem comprometer o estabelecimento e a sobrevivência da espécie. Níquel (Ni) é um nutriente essencial às plantas, mas níveis aumentados desse metal, em razão da poluição, podem causar efeitos deletérios, especialmente em macrófitas aquáticas. Testes de germinação de megásporos foram realizados usando-se solução de Meyer, em concentrações de 0 (controle); 0,05; 0,5; 1; 5; 10; 20; 30; 50; 100 mg L -1 de Ni. O desenvolvimento inicial de esporófitos apomíticos foi estudado usando-se soluções contendo 0 (controle) a 4,8 mg L -1 de Ni. Relação negativa significante foi observada entre diferentes concentrações de Ni e as taxas de germinação de megásporos/formação de esporófitos. Raízes primárias e folhas primárias e secundárias foram significantemente mais curtas a 3,2 e 4,8 mg L -1 de Ni, quando comparadas ao tratamento sem esse metal. Em 4,8 mg L -1 , folhas também apresentaram clorose e necrose. A introdução de poluentes com Ni no habitat natural de Regnellidium diphyllum pode inibir o estabelecimento de plantas em estádio inicial de desenvolvimento, um problemaa a ser consider...

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

“…Kieling-Rubio et al (2010) observed that 50 mg L −1 of hexavalent chromium also had a signifi cant negative impact on R. diphyllum germination. Th ose same authors later found that nickel also reduced R. diphyllum spore germination, although the germination rate at 100 mg L −1 was still 46%, higher than that observed here for the same concentration of copper (Kieling-Rubio et al 2012).…”

“…Hexavalent chromium has also been shown to be toxic to R. diphyllum, stunting the growth of roots and leaves, at concentrations ≥ 3.2 mg L −1 (Kieling-Rubio et al 2010). Kieling-Rubio et al (2012) found that the primary roots, primary leaves and secondary leaves of R. diphyllum were all signifi cantly shorter when grown in solutions with nickel concentrations of 3.2 or 4.8 mg L −1 than when grown in a nickel-free solution, and that the leaves of plants grown in the 4.8 mg L −1 solution exhibited chlorosis and necrosis.…”

“…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.…”

Lead tolerance and accumulation in initial sporophytes of Regnellidium diphyllum Lindm. (Marsileaceae)

“…Exposure to the same concentration of hexavalent chromium also caused a significant decrease in megaspore germination, which was approximately 25% (Kieling-Rubio et al, 2010). Increasing concentrations of nickel (0.05 to 100 mg L -1 ) were also associated with a decrease in germination percentage from 75 to 45% (Kieling-Rubio et al, 2012). Lower germination percentages (of approximately 49%) were also observed in megaspores exposed to 50 mg L -1 copper (Cassanego et al, 2013).…”

“…Hexavalent chromium was toxic for this species at concentrations at or above 3.2 mg L -1 , leading to reduction in root and leaf growth (Kieling-Rubio et al, 2010). The length of roots, primary and secondary leaves was also shorter in sporophytes exposed to nickel concentrations of 3.2 and 4.8 mg L -1 than in sporophytes not exposed to nickel (Kieling-Rubio et al, 2012). Cassanego et al (2013) observed significant negative effects on the development of R. diphyllum sporophytes grown in media with copper concentrations of 5 mg L -1 and higher.…”