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

Regnellidium diphyllum Lindm. is a heterosporous fern which grows in shallow waters and wetlands, and water pollution contributes to its vulnerability. Environmental lead contamination is mostly caused by industrial and agricultural residues as well as domestic sewage. Given its persistence in the environment, lead can cause important toxicity in living organisms. Megaspore germination and the initial growth of R. diphyllum sporophytes were assessed in Meyer's solution with lead nitrate (Pb(NO3)2) concentrations of 0 (control), 1, 5, 10 and 50 mg L–1. The study was conducted in a growth chamber at 25±1°C and a 12 hour photoperiod with a nominal irradiance of 100 μmol m–2 s–1, for 28 days. Lead concentration in sporophytes was assessed using atomic absorption spectrometry. In the absence of lead, 74% of spores germinated, while significantly lower germination percentages were observed in Pb(NO3)2 concentrations of 1, 10 and 50 mg L–1. The presence of lead did not significantly influence root growth. At 28 days, primary leaf development was significantly lower in Pb(NO3)2 concentrations of 5 mg L–1 and higher in relation to the control. The length of secondary leaves did not significantly differ between sporophytes exposed to different concentrations of lead and those of the control at 28 days. Sporophytes exposed to 10 and 50 mg L–1 Pb(NO3)2 accumulated 1129 mg kg–1 and 5145 mg kg–1 of Pb, respectively. The presence of high levels of lead in R. diphyllum sporophytes did not prevent initial development. Future studies should investigate the ability of the species to accumulate and tolerate high levels of lead in advanced stages of its development and in environmental conditions

Effects of 2,4-D on the germination of megaspores and initial development of Regnellidium diphyllum Lindman (Monilophyta, Marsileaceae) Efeitos do 2,4-D sobre a germinação de megásporos e o desenvolvimento inicial de Regnellidium diphyllum Lindman (Monilophyta, Marsileaceae)

Regnellidium diphyllum is considered as endangered, occurring in the State of Rio Grande do Sul, Brazil, and a few adjoining localities in Uruguay, Argentina and the State of Santa Catarina. It grows in wetlands frequently altered for agricultural activities. Herbicides based on 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used in these fields. The effects of 2,4-D on the germination of megaspores and initial sporophytic development of R. diphyllum were investigated. Six concentrations of 2,4-D (0.32; 0.64; 1.92; 4.80; 9.60 and 19.20 mg.L-1), and the control (0.00 mg.L-1), were tested in vitro, using Meyer's medium. Cultures were maintained in a growth chamber at 24 ± 1 °C, under artificial light with nominal irradiance of 110 µmol.m-2/s and 16 hours photoperiod. Megaspore germination was lower at 9.60 and 19.20 mg.L-1 of 2,4-D (56 and 48%, respectively), compared with the control (68%). Herbicide concentrations of up to 1.92 mg.L-1 did not significantly decrease the number of sporophytes formed. At 19.20 mg.L-1, no sporophytes were formed. The lengths of the primary root, primary and secondary leaves were greater at concentrations of 0.32 and 0.64 mg.L-1 of 2,4-D. Low concentrations of 2,4-D do not affect germination rates and initial development of R. diphyllum in a significant way. However, higher concentrations (9.60 and 19.20 mg.L-1) affect substantially the germination of the megaspores and interfere with the establishment of the species.Regnellidium diphyllum é considerada ameaçada, ocorrendo no Estado do Rio Grande do Sul, Brasil, e em algumas localidades vizinhas no Uruguai, na Argentina e no Estado de Santa Catarina. Cresce em áreas alagáveis, frequentemente alteradas para atividades agrícolas. Herbicidas baseados em ácido 2,4-diclorofenoxiacético (2,4-D) são largamente utilizados nestas plantações. Os efeitos do 2,4-D sobre a germinação de megásporos e o desenvolvimento esporofítico inicial de R. diphyllum foram investigados. Seis concentrações de 2,4-D (0,32; 0,64; 1,92; 4,80; 9,60 e 19,20 mg.L-1), além do controle (0,00 mg.L-1) foram testadas in vitro, utilizando meio de Meyer. As culturas foram mantidas em câmara de germinação a 24 ± 1 °C, sob luz artificial, com irradiância nominal de 110 mmol.m-2/s e fotoperíodo de 16 horas. A germinação de megásporos foi menor em 9,60 e 19,20 mg.L-1 de 2,4-D (56 e 48%, respectivamente), comparada ao controle (68%). Concentrações até 1,92 mg.L-1 não diminuíram significativamente o número de esporófitos formados. Em 19,20 mg.L-1, não houve formação de esporófitos. Os comprimentos da raiz primária e das folhas primária e secundária foram maiores em concentrações de 0,32 e 0,64 mg.L-1 de 2,4-D. Baixas concentrações de 2,4-D não afetam significantemente as taxas de germinação e o desenvolvimento inicial de R. diphyllum. Entretanto, maiores concentrações (9,60 e 19,20 mg.L-1) afetam substancialmente a germinação de megásporos e interferem no estabelecimento da espécie

Effects of 2,4-D on the germination of megaspores and initial development of Regnellidium diphyllum Lindman (Monilophyta, Marsileaceae)

Regnellidium diphyllum is considered as endangered, occurring in the State of Rio Grande do Sul, Brazil, and a few adjoining localities in Uruguay, Argentina and the State of Santa Catarina. It grows in wetlands frequently altered for agricultural activities. Herbicides based on 2,4-dichlorophenoxyacetic acid (2,4-D) are widely used in these fields. The effects of 2,4-D on the germination of megaspores and initial sporophytic development of R. diphyllum were investigated. Six concentrations of 2,4-D (0.32; 0.64; 1.92; 4.80; 9.60 and 19.20 mg.L-1), and the control (0.00 mg.L-1), were tested in vitro, using Meyer's medium. Cultures were maintained in a growth chamber at 24 ± 1 °C, under artificial light with nominal irradiance of 110 µmol.m-2/s and 16 hours photoperiod. Megaspore germination was lower at 9.60 and 19.20 mg.L-1 of 2,4-D (56 and 48%, respectively), compared with the control (68%). Herbicide concentrations of up to 1.92 mg.L-1 did not significantly decrease the number of sporophytes formed. At 19.20 mg.L-1, no sporophytes were formed. The lengths of the primary root, primary and secondary leaves were greater at concentrations of 0.32 and 0.64 mg.L-1 of 2,4-D. Low concentrations of 2,4-D do not affect germination rates and initial development of R. diphyllum in a significant way. However, higher concentrations (9.60 and 19.20 mg.L-1) affect substantially the germination of the megaspores and interfere with the establishment of the species

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

Regnellidium diphyllum Lindm. is a heterosporous fern which grows in shallow waters and wetlands, and water pollution contributes to its vulnerability. Environmental lead contamination is mostly caused by industrial and agricultural residues as well as domestic sewage. Given its persistence in the environment, lead can cause important toxicity in living organisms. Megaspore germination and the initial growth of R. diphyllum sporophytes were assessed in Meyer's solution with lead nitrate (Pb(NO3)2) concentrations of 0 (control), 1, 5, 10 and 50 mg L–1. The study was conducted in a growth chamber at 25±1°C and a 12 hour photoperiod with a nominal irradiance of 100 μmol m–2 s–1, for 28 days. Lead concentration in sporophytes was assessed using atomic absorption spectrometry. In the absence of lead, 74% of spores germinated, while significantly lower germination percentages were observed in Pb(NO3)2 concentrations of 1, 10 and 50 mg L–1. The presence of lead did not significantly influence root growth. At 28 days, primary leaf development was significantly lower in Pb(NO3)2 concentrations of 5 mg L–1 and higher in relation to the control. The length of secondary leaves did not significantly differ between sporophytes exposed to different concentrations of lead and those of the control at 28 days. Sporophytes exposed to 10 and 50 mg L–1 Pb(NO3)2 accumulated 1129 mg kg–1 and 5145 mg kg–1 of Pb, respectively. The presence of high levels of lead in R. diphyllum sporophytes did not prevent initial development. Future studies should investigate the ability of the species to accumulate and tolerate high levels of lead in advanced stages of its development and in environmental conditions

Biomonitoring of water genotoxicity in a Conservation Unit in the Sinos River Basin, Southern Brazil, using the <italic>Tradescantia</italic>micronucleus bioassay

The Tradescantia micronucleus (Trad-MCN) bioassay was used to investigate genotoxicity of water bodies in the Parque Municipal Henrique Luís Roessler (PMHLR), a conservation unit in the city of Novo Hamburgo, Southern Brazil, from November 2010 to October 2011. Every month, cuttings with young inflorescences of Tradescantia pallida var. purpurea were exposed for 24 hours to water collected at three sites in the park: (S1) head of the main stream; (S2) head of a secondary stream; (S3) a point past the junction of the two water bodies in which S1 and S2 were located. As a negative control, cuttings were exposed to distilled water for 24 h every quarter. Micronuclei (MCN) frequency was determined in young tetrads of pollen mother cells and described as MCN/100 tetrads. Rainfall data were also recorded. In nine months at S1 and S2, and in eleven months at S3, micronuclei frequencies were significantly higher than in quarterly controls, in which frequencies varied from 1.19 to 1.62.During sampling, no significant differences were found in MCN frequencies at S1, which ranged from 2.2 to 3.6. At the other sampling sites, there were significant differences between the months evaluated, and MCN frequencies ranged from 1.3 to 6.5 at S2 and from 2.3 to 5.2 at S3. There were no associations between rainfall and MCN frequencies at the three sampling sites. Tradescantia pallida var. purpureaconfirmed genotoxicity in the water bodies of the PMHLR, even at the head of the streams, which suggests that actions should be promoted to control anthropogenic effects in the streams of this conservation unit.</p