Germination and sporophytic development of Regnellidium diphyllum Lindm. (Marsileaceae) in the presence of a glyphosate-based herbicide

Abstract

Regnellidium diphyllum is a vulnerable heterosporous fern which occurs in the State of Rio Grande do Sul, Brazil, and in some neighboring localities in the State of Santa Catarina, in Uruguay and Argentina. The species grows in areas subjected to flooding and humid soils which frequently are alterated by agricultural activities. Agricultural fields are commonly treated with herbicides such as glyphosate. The effects of glyphosate on in vitro germination of megaspores and initial sporophytic development of R. diphyllum under aqueous conditions were investigated. Six glyphosate concentrations (0.32, 0.64, 1.92, 4.80, 9.60 and 19.20 mg/L) and the control (0.00 mg/L) were tested using Meyer’s medium. Cultures were maintained in vitro in a growth chamber at 24±1oC and 16 hours photoperiod for five weeks. Megaspore germination was significantly reduced (67% and lower) in concentrations of 4.80 mg/L onwards compared with the control (81%), while the sporophyte formation was negatively influenced even at the lowest concentration tested (0.32 mg/L). The length of the primary root and primary and secondary leaves was significantly reduced at glyphosate concentrations of 4.80 mg/L onwards. Low concentrations of the herbicide did not affect the percentage of germination, although significantly interfered in the initial development of R. diphyllum. Concentrations of 9.60 and 19.20 mg/L inhibited the establishment of new plants. These results indicate that application of glyphosate to agricultural areas may have negative impacts on the vulnerable fern R. diphyllum.