The impact of soil chloride concentration and salt type on the excretions of four recretohalophytes with different excretion mechanisms.

Four natives Canadian recretohalophytic species: Atriplex canescens, Armeria maritima, Spartina pectinata, and Distichlis spicata were examined to determine their relative uptake and excretion of chloride in the context of phytoremediation. Adult plants were grown in soils contaminated with either sodium chloride or potassium chloride at various concentrations, then manually washed to collect the excreted salts. Atriplex canescens which has salt bladders, was found to have negligible excretions, suggesting that these structures release minimal amounts of salt onto the leaf's surface. Chloride excretions of S. pectinata and D. spicata increased with higher soil chloride concentrations. A. maritima showed minimal excretion until a threshold soil salinity was reached. This species shifted from a reliance on internal sequestration to secretion at higher soil salinity. The salt used in the media did not impact these trends, but D. spicata excreted significantly more chloride under sodium chloride conditions. While all four species studied were able to translocate significant amount of salt to their shoots, only S. pectinata, D. spicata, and A. maritima are suitable candidates for remediation by haloconduction. Among these, A. maritima showed the greatest potential and significantly reduced the soil chloride concentration by up to 60% in the highest concentration treatment (4 mg/g).HIGHLIGHTSArmeria maritima, Spartina pectinata, and Distichlis spicata are suitable species for remediation via haloconduction.Armeria maritima had the highest total extraction capacity at high soil chloride.Spartina pectinata had the most consistent excretion capacity and is the most suitable for remediation of soils with lower soil chloride.

Curing the earth: A review of anthropogenic soil salinization and plant-based strategies for sustainable mitigation.

At low concentrations salts are relatively benign, but anthropogenic activities can drive concentrations to levels that impact soil quality, microbial, plant, and animal life. Soil and freshwater salinization are growing issues worldwide that are difficult to manage with conventional treatments. In this review, salt tolerant plants known as halophytes are evaluated for their potential to phytoremediate salinized soils and prevent leaching of salts into surface and ground water. While most plants are sensitive to high concentrations of salt in their growth media, halophytic plants have developed mechanisms to tolerate and thrive in these environments. Some plants exclude salts at the roots, others sequester salts in their central vacuole, while others secrete salts through specialized salt glands on their leaf surfaces. The extraction of salts from soil by both plants that sequester or secrete salts are reviewed as well as implementation strategies that could drive economic feasibility. Further, phytoremediation of salinized soils is considered in the context of a changing climate.

Assessing effects of legacy nuclear waste on plants: Sensitive fern (Onoclea sensibilis) gametophyte viability at the Chalk River site.

We evaluated the effects of chronic exposure to environmental radiological contamination on the reproductive fitness of sensitive fern (Onoclea sensibilis) by quantifying viability in haploid gametophytes of spores collected from ferns from background and contaminated areas of the Chalk River site. Dose rates measured in situ at field sites ranged from 60 to 849 µGy h-1, with effects possible at the more contaminated sites (greater than 400 µGy h-1). Fern spores were also irradiated from 1 to 1000 Gy to develop dose-response curves. We found no effects on gametophyte viability at the most contaminated areas of the Chalk River site, where we estimated growing season doses of 0.3-3.7 Gy. Dose-response curves show evidence of hormesis, with an increase in gametophyte viability up to 10 Gy, followed by a rapid decline to no viable gametophytes at doses of 1000 Gy. The sensitive fern is not a radiosensitive plant species, but effects do occur within the normal range (10-1000 Gy) of most plant species, making it useful as a sentinel species from a community perspective. Sensitive fern spore germination is high and stable over field dose ranges, with effects primarily on gametophyte viability. This method shows promise as an effects monitoring tool for sites with radiological contamination.