Metal effects on germination and seedling development in closely-related halophyte species inhabiting different elevations along the intertidal gradient.

Seed germination and seedling establishment are very sensitive plant stages to metal pollution. Many halophyte species colonizing salt marshes are able to germinate and establish in highly contaminated habitats and low marsh halophyte species seem to show higher tolerance to metals than high marsh species. We analyzed the effects of copper, zinc and nickel in concentrations up to 2000 µM on seed germination and seedling growth in two closely related species of Sarcocornia, S. perennis, a low marsh species, and S. fruticosa, a high marsh species. Germination of both halophytes was not affected by any metal concentration, and their seedling growth, mainly radicle length, was reduced by increasing metal concentrations. Seedlings of S. perennis showed higher tolerance to the three metals than those of S. fruticosa. Our results are useful for designing ecotoxicological bioassays and planning phytoremediation projects in salt marshes.

Effects of heavy metal pollution on germination and early seedling growth in native and invasive Spartina cordgrasses.

Seed germination and seedling establishment are the stages most sensitive to abiotic stress in the plant life cycle. We analyzed the effects of copper, zinc and nickel on seed germination and early seedling growth of native Spartina maritima and invasive S. densiflora from polluted and non-polluted estuaries. Germination percentages for either species were not affected by any metal at any tested concentration (up to 2000 µM). However, the increase in metal concentration had negative effects on S. densiflora seedlings. The primary effect was on radicle development, representing initial seedling emergence. Spartina densiflora seedlings emerging from seeds from Tinto Estuary, characterized by high bioavailable metal loads, showed higher tolerance to metals than those from less polluted Odiel and Piedras Estuaries. Comparing our results to metal concentrations in the field, we expect S. densiflora seedling development would be negatively impacted in the most metal-polluted areas in Odiel and Tinto Estuaries.