Lead tolerance and accumulation in the gametophytes of the fern Athyrium yokoscense

Abstract

The fern Athyrium yokoscense is known to be highly tolerant to lead toxicity, and is a lead hyperaccumulator that can accumulate over 1,000 microg g(-1) of lead in its dry matter. In this work, we examined whether the gametophytic generation of A. yokoscense also resists lead toxicity like the sporophytic generation. Spore germination in A. yokoscense was more tolerant to Pb2+, compared to that in other fern species, such as Pteridium aquilinum, Lygodium japonicum and Pteris vittata. In addition, the early gametophyte development of A. yokoscense was not much affected by 10 microM Pb2+, as evaluated from the prothallial growth and rhizoid development. We also showed that Athyrium gametophytes could accumulate more than 10,000 microg g(-1) of lead, and that the lead was localized in the cytosol and vacuole of rhizoidal cells, as determined by a transmission electron micrograph. These results indicate that Athyrium gametophytes have the ability to accumulate lead in the rhizoids. Furthermore, the gametophytes were found to include a large amount of proanthocyanidins (condensed tannins). Because proanthocyanidins have a latent ability to complex with lead ions, the possible roles of proanthocyanidins in the lead tolerance and accumulation of Athyrium gametophytes are discussed.

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

“…The concentration of lead in these sporophytes was, respectively, 100 and 500 times the concentration of the metal in the control sporophytes. Similar results have been obtained for the aquatic fern Azolla filiculoides, which presented concentrations of lead approximately 620% higher in specimens exposed to solution containing 20 mg L -1 lead for four days (Oren Benaroya et al, 2004) and for the terrestrial fern Athyrium yokoscense, which was found to accumulate 23000 mg kg -1 of lead in gametophytes grown for three weeks in solutions containing 2 mg L -1 Pb(CH 3 COO) 2 (Kamachi et al, 2005). The fact that lead was also detected in sporophytes in the control condition may be suggestive of contamination of the plant's natural environment.…”

“…& Sav.) Christ presented a comparable reduction in spore germination rates in the presence of 27 mg L -1 of lead (Kamachi et al, 2005). Contrary, the angiosperm Brassica pekinensis Rupr.…”

“…The area where sporocarps were collected in the Gravataí River Basin is used for agriculture, and particularly irrigated rice cultivation (Rio Grande do Sul, 2013). Therefore, significant amounts of fertilizer, herbicide and fungicide residues may be released in the environment, contributing to lead accumulation in plant reproductive structures (Kamachi et al, 2005;Hu et al, 2010). Furthermore, this area is near a national highway with heavy traffic, which has connected the north coast of the state of Rio Grande do Sul to its capital, Porto Alegre, since it was built in 1973 (CONCEPA, 2013).…”

A New Method of Environmental Assessment and Monitoring of Cu, Zn, As, and Pb Pollution in Surface Soil Using Terricolous Fruticose Lichens

“…The remaining Cladonia spp. and Cladia aggregata occurred mainly on humus soil and dead leaves, e.g., from ferns, such as Athyrium yokoscense, which are known as an accumulator and bioindicator for Cu, Zn, Cd, and/or Pb [38][39][40][41]. Cladonia spp.…”

A New Method of Environmental Assessment and Monitoring of Heavy Metal Polluted Soil Using Fruticose Lichens

“…The remaining Cladonia spp. and Cladia aggregata occurred mainly on humus soil and dead leaves, e.g., from ferns such as Athyrium yokoscense which are known as a resistant, accumulator, and bioindicator for Cu, Zn, Cd, and Pb [28][29][30][31]. Cladonia spp.…”