Phytotoxicity of sea-water aerosols on forest plants with special reference to the role of surfactants

Abstract

Experiments were conducted in a wind tunnel to investigate the impact of synthetic sea-water aerosols, with or without the addition of sodium linear-alkylbenzene-sulfonate (LAS), a common pollutant of sea-water, on young plants of Pinus pinea and Quercus ilex. LAS had a minor direct toxic effect, but its presence was correlated with a greater absorbance of salts into leaf tissues. Sodium was the principal noxious agent in Q. ilex; in P. pinea the contributions of sodium and chloride were not different. Potassium levels decreased in both species as a consequence of saline stress; the levels of calcium and magnesium did not show any major variation. By using a gradient of LAS concentrations in sea-water (from 0 to 240 ppm), it was possible to identify a significant linear regression for sodium and chloride absorbed by the leaves. Total free amino acid content was significantly increased by the saline treatment in P. pinea and a consistent accumulation of proline took place; no such metabolic changes were observed in Q. ilex, which proved to be more salt stress tolerant. An exposure for 10 days of plants to 110 ppb SO 2 (a concentration which does not cause any macroscopic injury) before and/or after the spray induced a significant increase in toxicity of the saline treatment.