Mature sporocarps were collected from plants in a natural population of Regnellidium diphyllum in the municipality of Gravatai (29[degrees]57'18"S, 51[degrees]1'52"W), in the state of Rio Grande do Sul, Brazil.
The experiment was conducted in a growth chamber at temperature of 25[+ or -]1[degrees]C, with a 12 hour photoperiod under fluorescent light with a nominal irradiance of 100 [micro]mol [m.sup.-2] [s.sup.-1], which are appropriate abiotic conditions for in vitro culture of Regnellidium diphyllum (Wunder et al., 2009; Droste et al., 2010).
Regnellidium diphyllum megaspore germination occurred under all concentrations of lead nitrate (Pb[(N[O.sub.3]).sub.2]) and in the control condition.
Although Regnellidium diphyllum was able to germinate in the presence of 50 mg [L.sup.-1] Pb[(N[O.sub.3]).sub.2], there was a 30% reduction in germination percentage compared to the control condition.
Root apex structure in Regnellidium diphyllum
The heterosporous fern Regnellidium diphyllum Lindman occurs in southern Brazil and some adjoining localities in Uruguay and Argentina (Schultz, 1949; Alonso-Paz and Bassagoda, 2002) and figures on the endangered species list of the state of Rio Grande do Sul, Brazil (Rio Grande do Sul, 2011).
The aim of this study was to investigate germination of megaspores and initial development of sporophytes of Regnellidium diphyllum in the presence of nickel, providing information on the influence of this metal in the establishment and growth of the species.
Mature sporocarps of Regnellidium diphyllum were obtained from different plants in the municipality of Viamao (30[degrees] 05' 00" S and 50[degrees] 47' 00" W, Rio Grande do Sul state, Brazil) and kept at room temperature (about 25 [degrees]C).
(1981) Tropisms in Regnellidium diphyllum
. Fern Gazette 12, 131-132.
Regnellidium diphyllum Lindman, a heterosporous fern in the Marsileaceae family, has its distribution restricted to Southern Brazil and some adjoining localities in Uruguay and Argentina (Schultz, 1949; Alonso-Paz and Bassagoda, 2002).
Mature sporocarps of Regnellidium diphyllum were obtained from different plants collected in the municipality of Triunfo (State of Rio Grande do Sul, Brazil) and kept at room temperature (about 25 [degrees]C) until the beginning of the experiment, one month later.
Vianna (1973) verified that the first sporophytic structures emerged from the megagametophytes of Regnellidium diphyllum around the first week of in vitro culture.