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

摘要

Regnellidium diphyllum Lindm. is a heterosporous fern growing in wetlands and humid soils that are being converted to agricultural activities. Many products that are used in agriculture contain copper, resulting in surface and groundwater contamination. Germination and initial development tests were performed using Meyer's solution containing copper sulphate at concentrations of 0 (control), 1, 5, 10, 50 and 100 mg L-1. The experiment was conducted in a growth chamber at 25 ± 1oC for 28 days, with a 12/12-hour light/dark cycle and a photon flux density of 100 μmol m-2 s-1. The lowest germination rate (6%) was observed at 100 mg L-1. Primary root growth was significantly reduced at > 10 mg L-1. Secondary leaves of sporophytes grown in concentrations > 5 mg L-1 were progressively shorter than were those formed by the control plants. We conclude that the release of pollutants containing copper into the natural habitats of R. diphyllum can cause phytotoxicity, threatening the establishment of populations and worsening the already vulnerable conservation status of this species.